Secondary battery and battery pack

Abstract

Provided is a secondary battery excellent in reliability. This secondary battery comprises an electrode winding body, a first electrode current collector plate, and a second electrode current collector plate. In the electrode winding body, a laminate including a first electrode, a second electrode, and a separator is wound along a longitudinal direction of the laminate, wherein there is a through hole penetrating therethrough in a width direction orthogonal to the longitudinal direction. The first electrode current collector plate and the second electrode current collector plate face each other across the electrode winding body in the width direction. The first electrode current collector plate has an opening at a position overlapping with the through hole in the width direction. The diameter of the opening is smaller than the diameter of the through hole.

Description

Secondary batteries and battery packs

[0001] The present disclosure relates to a secondary battery and a battery pack including the same.

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as power sources that are small, lightweight, and capable of achieving high energy density. These secondary batteries include a battery element housed inside an exterior member, and various studies have been conducted on the configuration of such secondary batteries (see, for example, Patent Document 1).

[0003] Patent Document 1 proposes a secondary battery that employs a so-called tabless structure to reduce internal resistance and enable charging and discharging with a relatively large current.

[0004] International Publication No. 2021 / 020237

[0005] Various studies have been conducted to improve the performance of secondary batteries, but there is still room for improvement in the reliability of secondary batteries.

[0006] Therefore, a highly reliable secondary battery is desired.

[0007] A first secondary battery according to an embodiment of the present disclosure includes an electrode winding, a first electrode current collector, and a second electrode current collector. The electrode winding is formed by winding a laminate including a first electrode, a second electrode, and a separator along the longitudinal direction of the laminate, and has a through-hole penetrating the laminate in a width direction perpendicular to the longitudinal direction. The first electrode current collector and the second electrode current collector face each other, sandwiching the electrode winding in the width direction. The first electrode current collector includes an opening at a position overlapping the through-hole in the width direction. The diameter of the opening is smaller than the diameter of the through-hole.

[0008] A second secondary battery according to an embodiment of the present disclosure includes an electrode winding, a first electrode current collector, and a second electrode current collector. The electrode winding is formed by winding a laminate including a first electrode, a second electrode, and a separator along the longitudinal direction of the laminate, and has a through-hole penetrating the laminate in a width direction perpendicular to the longitudinal direction. The first electrode current collector and the second electrode current collector face each other with the electrode winding sandwiched between them in the width direction. A second bent portion bent toward the second electrode current collector is provided at the outer peripheral edge of the first electrode current collector.

[0009] A third secondary battery according to an embodiment of the present disclosure includes an electrode winding, a first electrode current collector, and a second electrode current collector. The electrode winding is formed by winding a laminate including a first electrode, a second electrode, and a separator along the longitudinal direction of the laminate, and has a through-hole extending through the laminate in a width direction perpendicular to the longitudinal direction. The first electrode current collector and the second electrode current collector face each other, sandwiching the electrode winding in the width direction. The first electrode includes a first electrode current collector, an undercoat layer covering the first electrode current collector, and a first electrode active material layer covering a portion of the undercoat layer. The second electrode includes a second electrode current collector and a second electrode active material layer covering the second electrode current collector. In the width direction, an edge of the first electrode active material layer is positioned recessed from an edge of the undercoat layer, and an edge of the second electrode active material layer is positioned between an edge of the undercoat layer and an edge of the first electrode active material layer.

[0010] According to the first to third secondary batteries of an embodiment of the present disclosure, high reliability can be achieved.

[0011] FIG. 1 is a cross-sectional view illustrating an example of a vertical cross-sectional structure along the height direction of a secondary battery according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram illustrating an example of a laminate including a positive electrode, a negative electrode, and a separator illustrated in FIG. 1. FIG. 3 is a cross-sectional view illustrating an example of a horizontal cross-sectional structure of the electrode winding illustrated in FIG. 1. FIG. 4A is a developed view of the positive electrode illustrated in FIG. 1. FIG. 4B is a cross-sectional view of the positive electrode illustrated in FIG. 1. FIG. 5A is a developed view of the negative electrode illustrated in FIG. 1. FIG. 5B is a cross-sectional view of the negative electrode illustrated in FIG. 1. FIG. 6A is a plan view of the positive electrode current collector illustrated in FIG. 1. FIG. 6B is a plan view of the negative electrode current collector illustrated in FIG. 1. FIG. 7 is a perspective view illustrating a manufacturing process of the secondary battery illustrated in FIG. 1. FIG. 8 is a block diagram illustrating a circuit configuration of a battery pack to which the secondary battery according to an embodiment of the present disclosure is applied. FIG. 9A is a schematic cross-sectional view illustrating a partial configuration of a positive electrode according to Aspect 1-2. FIG. 9B is a schematic cross-sectional view illustrating a partial configuration of a positive electrode according to Aspect 1-3. FIG. 9C is a cross-sectional view schematically illustrating an enlarged view of a positive electrode active material particle of Aspect 1-4. FIG. 10A is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode of Aspect 2-1-1. FIG. 10B is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode of Aspect 2-1-2. FIG. 10C is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode of Aspect 2-1-3. FIG. 10D is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode of Aspect 2-1-4. FIG. 11A is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode of Aspect 2-2-1. FIG. 11B is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode of Aspect 2-2-2. FIG. 12A is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode of Aspect 2-3-1. FIG. 12B is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode of Aspect 2-3-2. FIG. 13 is a cross-sectional view schematically illustrating the configuration of a portion of a positive electrode active material layer of Aspect 2-4. FIG. 14 is a cross-sectional schematic diagram showing the configuration of a positive electrode current collector of Aspect 2-6. FIG. 15 is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode of Aspect 3-1. FIG. 16A is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode of Aspect 4-1. FIG. 16B is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode of Aspect 4-2. FIG. 16C is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode of Aspect 4-3. FIG. 17 is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode of Aspect 4-4-1. FIG. 18A is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode of Aspect 4-4-2A.FIG. 18B is an enlarged cross-sectional view showing a partial configuration of the positive electrode of Aspect 4-4-2B. FIG. 19A is an enlarged cross-sectional view showing a partial configuration of the positive electrode of Aspect 4-4-3A. FIG. 19B is an enlarged cross-sectional view showing a partial configuration of the positive electrode of Aspect 4-4-3B. FIG. 20 is an enlarged cross-sectional view showing a partial configuration of the positive electrode of Aspect 4-5. FIG. 21A is an enlarged cross-sectional view showing a partial configuration of the positive electrode of Aspect 4-6A. FIG. 21B is an enlarged cross-sectional view showing a partial configuration of the positive electrode of Aspect 4-6B. FIG. 21C is an enlarged cross-sectional view showing a partial configuration of the positive electrode of Aspect 4-6C. FIG. 22A is a schematic plan view showing a partial configuration of the positive electrode of Aspect 4-7A. FIG. 22B is a schematic plan view showing a partial configuration of the positive electrode of Aspect 4-7B. FIG. 23A is a schematic cross-sectional view showing a partial configuration of the wound electrode body of Aspect 4-8A. FIG. 23B is a schematic cross-sectional view showing a partial configuration of the wound electrode body of Aspect 4-8C. FIG. 23C is a cross-sectional schematic diagram showing the configuration of a portion of the wound electrode body of Aspect 4-8C. FIG. 24 is an enlarged cross-sectional view showing the configuration of a portion of the positive electrode of Aspect 4-9. FIG. 25 is an enlarged cross-sectional view showing the configuration of a portion of the positive electrode of Aspect 4-10. FIG. 26 is an enlarged cross-sectional view showing the configuration of a portion of the positive electrode of Aspect 4-11. FIG. 27 is an enlarged cross-sectional view showing the configuration of a portion of the positive electrode of Aspect 4-13. FIG. 28A is an enlarged cross-sectional view showing the configuration of a portion of the positive electrode of Aspect 4-14. FIG. 28B is a characteristics diagram showing the relationship between the presence or absence of a carbon coating layer and the interfacial resistance between the positive electrode current collector and the positive electrode active material layer. FIG. 29A is an enlarged cross-sectional view showing the configuration of a portion of the wound electrode body of Aspect 4-15-1. FIG. 29B is an enlarged cross-sectional view showing the configuration of a portion of the wound electrode body of Aspect 4-15-2. FIG. 29C is an enlarged cross-sectional view showing the configuration of a portion of the wound electrode body of Aspect 4-15-3. FIG. 30 is an enlarged cross-sectional view and a schematic plan view showing the configuration of the positive electrode of Aspect 4-16. Fig. 31 is a schematic diagram showing positive electrode active material particles and polyvinylidene fluoride contained in the positive electrode active material layer of Aspect 5-1. Fig. 32 is a schematic diagram showing a positive electrode of Aspect 5-2, and positive electrode active material particles and polyvinylidene fluoride contained in the positive electrode active material layer. Fig. 33 is a cross-sectional schematic diagram showing a positive electrode of Aspect 5-3. Fig. 34 is a cross-sectional schematic diagram showing a positive electrode of Aspect 5-4. Fig. 35 is a cross-sectional schematic diagram showing an electrode wound body of Aspect 5-5. Fig. 36 is a cross-sectional schematic diagram showing an electrode wound body of Aspect 5-6.FIG. 37A is a cross-sectional schematic diagram showing a positive electrode of Aspect 5-7-1. FIG. 37B is a cross-sectional schematic diagram showing a positive electrode of Aspect 5-7-2. FIG. 38A is a cross-sectional schematic diagram showing an electrode wound body of Aspect 5-8. FIG. 38B is a plan view of a developed positive electrode of the electrode wound body of Aspect 5-8. FIG. 39 is a cross-sectional schematic diagram showing an electrode wound body of Aspect 5-9. FIG. 40A is a schematic diagram showing negative electrode active material particles and porous CMC contained in the negative electrode active material layer of Aspect 6-1. FIG. 40B is a micrograph showing an enlarged view of negative electrode active material particles and porous CMC contained in the negative electrode active material layer of Aspect 6-2. FIG. 40C is a cross-sectional schematic diagram showing a negative electrode of Aspect 6-3. FIG. 41 is a cross-sectional schematic diagram showing an electrode wound body of Aspect 7-1. FIG. 42 is a cross-sectional schematic diagram showing an electrode wound body of Aspect 7-4. FIG. 43A is an enlarged cross-sectional view of the upper end portion in the height direction of the electrode winding of Aspect 7-6. FIG. 43B is an enlarged cross-sectional view of the lower end portion in the height direction of the electrode winding of Aspect 7-6. FIG. 44 is a cross-sectional view showing the vicinity of the upper end face of the electrode winding of a secondary battery of Aspect 8-2. FIG. 45A is a cross-sectional view showing the vicinity of the upper end face of the electrode winding of a secondary battery of Aspect 8-3-1. FIG. 45B is a cross-sectional view showing the vicinity of the upper end face of the electrode winding of a secondary battery of Aspect 8-3-2. FIG. 45C is a cross-sectional view showing the vicinity of the upper end face of the electrode winding of a secondary battery of Aspect 8-3-3. FIG. 45D is a cross-sectional view showing the vicinity of the upper end face of the electrode winding of a secondary battery of Aspect 8-3-4. FIG. 46A is a cross-sectional view showing the vicinity of the upper end face of the electrode winding of a secondary battery of Aspect 8-4-1. Fig. 46B is a cross-sectional schematic diagram showing the vicinity of the upper end surface of the electrode winding in a secondary battery of Aspect 8-4-2. Fig. 46C is a cross-sectional schematic diagram showing the vicinity of the upper end surface of the electrode winding in a secondary battery of Aspect 8-4-3. Fig. 47A is a cross-sectional schematic diagram showing the vicinity of the upper end surface of the electrode winding in a secondary battery of Aspect 8-5-1. Fig. 47B is a cross-sectional schematic diagram showing the vicinity of the upper end surface of the electrode winding in a secondary battery of Aspect 8-5-2. Fig. 48 is a plan view schematic diagram showing the electrode winding and positive electrode current collector plate in a secondary battery of Aspect 8-6. Fig. 49A is a plan view schematic diagram showing the electrode winding in an unfolded state in Aspect 10-3-1.FIG. 49B is a schematic plan view showing the electrode winding of Aspect 10-3-2 in an unfolded state. FIG. 50A is a schematic plan view showing the electrode winding of Aspect 10-4-1 in an unfolded state. FIG. 50B is a schematic plan view showing the electrode winding of Aspect 10-4-2 in an unfolded state. FIG. 51 is a perspective view showing the appearance of the electrode winding of Aspect 10-5. FIG. 52 is a schematic cross-sectional view showing the electrode winding and center pin of Aspect 10-6. FIG. 53 is a schematic cross-sectional view showing the center pin of Aspect 10-7. FIG. 54A is a schematic perspective view showing the appearance of the outer can of Aspect 13-2. FIG. 54B is a schematic perspective view showing the appearance of the outer can of Aspect 13-3. FIG. 54C is a schematic perspective view showing the appearance of the outer can of Aspect 13-4.

[0012] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order: A. Secondary battery A-1. Configuration A-2. Operation A-3. Manufacturing method B. Application example B-1. Battery pack B-2. Power storage system C. Particulars

[0013] A. Secondary Battery First, a secondary battery according to an embodiment of the present disclosure will be described.

[0014] In this embodiment, a cylindrical lithium-ion secondary battery having a cylindrical external shape will be described as an example. However, the secondary battery of the present disclosure is not limited to a cylindrical lithium-ion secondary battery, and may be a lithium-ion secondary battery having an external shape other than a cylindrical shape, or a secondary battery using an electrode reactant other than lithium.

[0015] The charge / discharge principle of a secondary battery is not particularly limited, but the following describes a case where battery capacity is obtained by utilizing the absorption and desorption of an electrode reactant. This secondary battery includes a positive electrode, a negative electrode, and an electrolyte. In this secondary battery, the charge capacity of the negative electrode is set to be larger than the discharge capacity of the positive electrode to prevent the electrode reactant from depositing on the surface of the negative electrode during charging. In other words, the electrochemical capacity per unit area of ​​the negative electrode is set to be larger than the electrochemical capacity per unit area of ​​the positive electrode.

[0016] The type of electrode reactant is not particularly limited as described above, but specifically includes light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, and alkaline earth metals include beryllium, magnesium, and calcium.

[0017] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

[0018] [A-1. Configuration] (Lithium-ion secondary battery 1) Fig. 1 shows a vertical cross-sectional configuration along the height direction of a lithium-ion secondary battery 1 (hereinafter simply referred to as secondary battery 1) according to this embodiment. The secondary battery 1 shown in Fig. 1 includes a substantially cylindrical outer can 11 and an electrode winding body 20 as a battery element housed in the outer can 11. Furthermore, the secondary battery 1 includes an outer tube 50 that covers the outer peripheral surface of the outer can 11. In this specification, the height direction of the secondary battery 1 is defined as the Z-axis direction.

[0019] Specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12, 13, an electrode winding 20, a positive electrode current collector 24 as a first electrode current collector, and a negative electrode current collector 25 as a second electrode current collector, all inside an outer can 11. The electrode winding 20 is a structure in which, for example, a positive electrode 21 and a negative electrode 22 are stacked and wound with a separator 23 interposed therebetween. The electrode winding 20 is impregnated with an electrolytic solution, which is a liquid electrolyte. The secondary battery 1 may further include, inside the outer can 11, one or more of a thermosensitive resistor (also referred to as a PTC element) and a reinforcing member.

[0020] (Outer can 11) The outer can 11 is a container that houses the positive electrode current collector 24, the negative electrode current collector 25, the electrode winding 20, and the like. The outer can 11 has a bottom 11B and a sidewall 11W. The bottom 11B also serves as a negative electrode terminal that is connected to the negative electrode 22 via the negative electrode current collector 25. The outer can 11 has, for example, a hollow cylindrical structure with a closed lower end in the Z-axis direction and an open upper end. Therefore, the upper end of the outer can 11 is an open end 11N, and the lower end of the outer can 11 is closed by a substantially disk-shaped bottom 11B. Between the open end 11N and the bottom 11B is a sidewall 11W that surrounds the electrode winding 20. The side wall portion 11W extends in the height direction along the outer edge of the bottom portion 11B to surround the electrode winding body 20, and includes an open end portion 11N on the opposite side of the bottom portion 11B, which is open and allows the electrode winding body 20 to be inserted therethrough. The outer can 11 is made of a metal material such as iron. However, the surface of the outer can 11 may be plated with a metal material such as nickel. The insulating plates 12 and 13 are disposed opposite each other in the Z-axis direction, for example, with the electrode winding body 20 sandwiched therebetween. In this specification, the open end portion 11N and its vicinity in the Z-axis direction may be referred to as the upper portion of the secondary battery 1, and the portion where the outer can 11 is closed and its vicinity may be referred to as the lower portion of the secondary battery 1.

[0021] (Outer tube 50) The outer tube 50 surrounds the side surface 11WS, which is the outer surface of the side wall portion 11W of the outer can 11. However, as shown in Fig. 1 , the outer tube 50 may also cover a folded portion 11P (described later) at the upper end of the outer can 11. The outer tube 50 may also cover a portion of the bottom surface 11BS, which is the outer surface of the bottom portion 11B of the outer can 11. The outer tube 50 is made of a heat-shrinkable insulating film containing, for example, a polyester-based resin, a polyamide-based resin, or a thermoplastic elastomer resin.

[0022] (Washer 55) A washer 55 is provided in the gap between the exterior tube 50 and the bent portion 11P of the exterior can 11. The washer 55 is an insulating ring member having an opening 55K in the central region within a plane perpendicular to the height direction. The protrusion 14T in the central region of the battery lid 14 is inserted into the opening 55K. The washer 55 can be made of, for example, black modified polyphenylene ether.

[0023] (Insulating Plates 12, 13) Each of the insulating plates 12, 13 is, for example, a dish-shaped plate having a surface perpendicular to the central axis CL of the electrode winding body 20, i.e., a surface perpendicular to the Z-axis in Fig. 1. The insulating plates 12, 13 are arranged so as to sandwich the electrode winding body 20 therebetween.

[0024] (Crimped structure 11R) The open end 11N of the exterior can 11 has a structure in which, for example, the battery lid 14 and the safety valve mechanism 30 are crimped via a gasket 15, i.e., a crimped structure 11R. The battery lid 14 seals the exterior can 11 with the electrode wound body 20 and other components housed inside the exterior can 11. The crimped structure 11R has a folded portion 11P as a so-called crimp portion. In addition, a constricted portion 11S is provided between the folded portion 11P and the insulating plate 12, where a portion of the exterior can 11 protrudes inward.

[0025] (Battery Lid 14) The battery lid 14 is primarily a closing member that closes the open end 11N when the electrode winding body 20 and other components are housed inside the exterior can 11. The battery lid 14 is, for example, a conductor containing the same material as the material from which the exterior can 11 is formed. The battery lid 14 closes the open end 11N of the exterior can 11 and is connected to the positive electrode current collector 24. Therefore, the battery lid 14 also serves as a positive electrode terminal that is connected to the positive electrode 21 via the positive electrode current collector 24. A protrusion 14T in the central region of the battery lid 14 protrudes upward (in the +Z direction), for example. As a result, the peripheral region of the battery lid 14 other than the central region is in contact with, for example, the safety valve mechanism 30.

[0026] (Gasket 15) The gasket 15 is a sealing member interposed primarily between the folded portion 11P of the outer can 11 and the battery lid 14. The gasket 15 seals the gap between the folded portion 11P and the battery lid 14. However, the surface of the gasket 15 may be coated with, for example, asphalt. The gasket 15 contains, for example, one or more insulating materials. The type of insulating material is not particularly limited, but examples include polymeric materials such as polybutylene terephthalate (PBT) and polypropylene (PP). Among these, polybutylene terephthalate is preferred as the insulating material. This is because the gap between the folded portion 11P and the battery lid 14 is sufficiently sealed while electrically isolating the outer can 11 and the battery lid 14 from each other.

[0027] (Safety valve mechanism 30) The safety valve mechanism 30 is mainly configured to release the internal pressure of the outer can 11 by releasing the sealed state of the outer can 11 as necessary when the pressure inside the outer can 11 (internal pressure) increases. The internal pressure of the outer can 11 may increase, for example, due to gas generated by a decomposition reaction of the electrolyte during charging and discharging. The internal pressure of the outer can 11 may also increase due to external heating.

[0028] (Electrode winding body 20) The electrode winding body 20 is disposed between the positive electrode current collector plate 24 and the negative electrode current collector plate 25. The electrode winding body 20 has an upper end face 41 that faces the positive electrode current collector plate 24 in the height direction, and a lower end face 42 that faces the negative electrode current collector plate 25 in the height direction. The electrode winding body 20 is a power generation element that causes charge / discharge reactions to proceed, and is housed inside the outer can 11. The electrode winding body 20 includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolytic solution that is a liquid electrolyte.

[0029] FIG. 2 is a developed view of the electrode winding body 20, and schematically illustrates a portion of a laminate S20 including a positive electrode 21 as a first electrode, a negative electrode 22 as a second electrode, and a separator 23. In the laminate S20 obtained by developing the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 interposed therebetween. The separator 23 includes, for example, two substrates, namely, a first separator member 23A and a second separator member 23B. Thus, the electrode winding body 20 includes a four-layer laminate S20 in which the positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are stacked in this order. The positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are all substantially strip-shaped members with the W direction as the short side and the L direction as the long side.

[0030] As shown in FIG. 3 , the electrode winding body 20 is formed by winding the laminate S20 around a through-hole 26 along a central axis CL extending in the Z-axis direction so as to form a spiral shape in a horizontal cross section perpendicular to the Z-axis direction. The laminate S20 is wound in an orientation in which the W direction roughly coincides with the Z-axis direction. Note that FIG. 3 illustrates an example configuration of the electrode winding body 20 along a horizontal cross section perpendicular to the Z-axis direction. However, in FIG. 3 , the separator 23 is omitted for improved visibility. The electrode winding body 20 has an overall substantially cylindrical appearance. The positive electrode 21 and the negative electrode 22 are wound while maintaining a state in which they face each other via the separator 23. A through-hole 26 is formed at the center of the electrode winding body 20 as an internal space. The through-hole 26 is a hole for inserting a winding core for assembling the electrode winding body 20 and an electrode rod for welding. The through-hole 26 extends in the Z-axis direction along the central axis CL and penetrates the electrode winding body 20. Therefore, the laminate S20 is wound around the through-hole 26.

[0031] The positive electrode 21, the negative electrode 22, and the separator 23 are wound such that the separator 23 is disposed at the outermost and innermost peripheries of the electrode winding body 20, respectively. At the outermost periphery of the electrode winding body 20, the negative electrode 22 is disposed outside the positive electrode 21. That is, as shown in FIG. 3 , a positive electrode outermost periphery portion 21out, which is located at the outermost periphery of the positive electrode 21 included in the electrode winding body 20, is disposed inside a negative electrode outermost periphery portion 22out, which is located at the outermost periphery of the negative electrode 22 included in the electrode winding body 20. Here, the positive electrode outermost periphery portion 21out is the outermost one-round portion of the positive electrode 21 in the electrode winding body 20. The negative electrode outermost periphery portion 22out is the outermost one-round portion of the negative electrode 22 in the electrode winding body 20. Meanwhile, at the innermost periphery of the electrode winding body 20, the negative electrode 22 is disposed inside the positive electrode 21. That is, as shown in Fig. 3, the negative electrode innermost circumferential portion 22in, which is located at the innermost periphery of the negative electrode 22 included in the electrode winding body 20, is located inside the positive electrode innermost circumferential portion 21in, which is located at the innermost periphery of the positive electrode 21 included in the electrode winding body 20. Here, the positive electrode innermost circumferential portion 21in is the innermost one-circumferential portion of the positive electrode 21 in the electrode winding body 20. The negative electrode innermost circumferential portion 22in is the innermost one-circumferential portion of the negative electrode 22 in the electrode winding body 20. The number of windings of each of the positive electrode 21, the negative electrode 22, and the separator 23 is not particularly limited and can be set as desired.

[0032] FIG. 4A is a developed view of the positive electrode 21, schematically illustrating the state before winding. FIG. 4B illustrates a cross-sectional configuration of the positive electrode 21. However, FIG. 4B illustrates a cross-section of the positive electrode 21 taken along line IVB-IVB in FIG. 4A . The positive electrode 21 includes a positive electrode current collector 21A, a positive electrode active material layer 21B, and an insulating layer 101. The positive electrode active material layer 21B may be provided, for example, on only one side of the positive electrode current collector 21A, or on both sides of the positive electrode current collector 21A. FIG. 4B illustrates a case in which the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. More specifically, the positive electrode current collector 21A includes a positive electrode current collector inner peripheral surface 21A1 facing the central axis CL and a positive electrode current collector outer peripheral surface 21A2 opposite the positive electrode current collector inner peripheral surface 21A1. The positive electrode 21 has, as the positive electrode active material layer 21B, a positive electrode inner periphery side active material layer 21B1 covering at least a portion of the positive electrode current collector inner periphery surface 21A1, and a positive electrode outer periphery side active material layer 21B2 covering at least a portion of the positive electrode current collector outer periphery surface 21A2. In this specification, the positive electrode inner periphery side active material layer 21B1 and the positive electrode outer periphery side active material layer 21B2 may be collectively referred to as the positive electrode active material layer 21B without distinguishing between them. The positive electrode active material layer 21B extends in both the L direction and the W direction perpendicular to the L direction. The L direction is the winding direction of the laminate S20. The W direction substantially coincides with the central axis CL.

[0033] The positive electrode current collector 21A includes a positive electrode covering region 211 covered by the positive electrode active material layer 21B and a positive electrode exposed region 212 extending in the W direction and not covered by the positive electrode active material layer 21B. The insulating layer 101 extends in the L direction along a first edge 21BT1 of the positive electrode active material layer 21B located at the boundary K between the positive electrode covering region 211 and the positive electrode exposed region 212. In the positive electrode 21 of this embodiment, as shown in FIG. 4B , the first edge 21BT1 of the positive electrode active material layer 21B is an inclined surface, and the insulating layer 101 is in contact with the first edge 21BT1. That is, the insulating layer 101 is formed so as to cover the vicinity of the first edge 21BT1 of the positive electrode active material layer 21B.

[0034] As shown in FIG. 4A , the positive electrode covering region 211 and the positive electrode exposed region 212 each extend along the L direction from the winding center edge 21E1 of the positive electrode 21 to the winding outer edge 21E2. That is, in the positive electrode 21, the positive electrode active material layer 21B covers the positive electrode current collector 21A from the winding center edge 21E1 of the positive electrode 21 to the winding outer edge 21E2 of the positive electrode 21 in the winding direction of the electrode wound body 20. The positive electrode covering region 211 and the positive electrode exposed region 212 are adjacent to each other in the W direction, which is the short-side direction of the positive electrode 21. Note that FIGS. 4A and 4B schematically illustrate the positive electrode current collector 21A extending linearly along the W direction. However, in reality, the positive electrode edge 212E of the positive electrode exposed region 212 is bent toward the central axis CL as shown in FIG. 1 and connected to the positive electrode current collector 24. That is, the end of the positive electrode exposed region 212 in the W direction forms the upper end surface 41 and is connected to the positive electrode current collector plate 24 (see FIG. 1 ). The upper end surface 41 is formed by bending the positive electrode edge portion 212E of the positive electrode exposed region 212 toward the through hole 26 in a wound state.

[0035] An insulating layer 101 may be provided near the boundary between the positive electrode covering region 211 and the positive electrode exposed region 212. Similar to the positive electrode covering region 211 and the positive electrode exposed region 212, the insulating layer 101 may extend from the winding center edge 21E1 to the winding outer edge 21E2 of the electrode winding body 20. The insulating layer 101 may be bonded to at least one of the first separator member 23A and the second separator member 23B. This is because misalignment between the positive electrode 21 and the separator 23 can be prevented. The insulating layer 101 may include a resin containing polyvinylidene fluoride (PVDF). The PVDF content of the insulating layer 101 allows the insulating layer 101 to swell with, for example, a solvent contained in the electrolyte solution, thereby enabling good adhesion to the separator 23.

[0036] FIG. 5A is a developed view of the negative electrode 22, schematically illustrating the state before winding. FIG. 5B illustrates a cross-sectional configuration of the negative electrode 22. Note that FIG. 5B illustrates a cross section taken along line VB-VB in FIG. 5A as viewed from the arrow direction. The negative electrode 22 includes, for example, a negative electrode current collector 22A as a second electrode current collector and a negative electrode active material layer 22B that covers a portion of the negative electrode current collector 22A. The negative electrode active material layer 22B may be provided on only one surface of the negative electrode current collector 22A, or on both surfaces of the negative electrode current collector 22A. FIG. 5B illustrates a case in which the negative electrode active material layer 22B is provided on both surfaces of the negative electrode current collector 22A. More specifically, the negative electrode current collector 22A includes a negative electrode current collector inner peripheral surface 22A1 facing the winding center of the electrode wound body 20, i.e., facing the central axis CL, and a negative electrode current collector outer peripheral surface 22A2 facing the side opposite the winding center of the electrode wound body 20, i.e., on the opposite side of the negative electrode current collector inner peripheral surface 22A1. The negative electrode 22 has, as the negative electrode active material layer 22B, a negative electrode inner peripheral side active material layer 22B1 covering at least a portion of the negative electrode current collector inner peripheral surface 22A1, and a negative electrode outer peripheral side active material layer 22B2 covering at least a portion of the negative electrode current collector outer peripheral surface 22A2. Note that in this specification, the negative electrode inner peripheral side active material layer 22B1 and the negative electrode outer peripheral side active material layer 22B2 may be collectively referred to as the negative electrode active material layer 22B without distinguishing between them.

[0037] The negative electrode 22 has a negative electrode covering region 221 in which the negative electrode current collector 22A is covered with the negative electrode active material layer 22B, and a negative electrode exposed region 222 in which the negative electrode current collector 22A is exposed and not covered with the negative electrode active material layer 22B. As shown in FIG. 5A , the negative electrode covering region 221 and the negative electrode exposed region 222 each extend along the L direction, which is the longitudinal direction of the negative electrode 22. The negative electrode exposed region 222 extends from the central axis side edge 22E1 to the outer peripheral edge 22E2 of the negative electrode 22 in the winding direction of the electrode wound body 20. In contrast, the negative electrode covering region 221 is not provided on the central axis side edge 22E1 or the outer peripheral edge 22E2 of the negative electrode 22. As shown in FIG. 5A , parts of the negative electrode exposed region 222 are formed to sandwich the negative electrode covering region 221 in the L direction, which is the longitudinal direction of the negative electrode 22. Specifically, the negative electrode exposed region 222 includes a first portion 222A, a second portion 222B, and a third portion 222C. The negative electrode 22 further has a lower edge 22E3 extending in the L direction on the lower side of the electrode winding body 20. The first portion 222A is provided adjacent to the negative electrode covering region 221 in the W direction and extends in the L direction from the central axis side edge 22E1 to the outer peripheral side edge 22E2 of the negative electrode 22. That is, the first portion 222A is a region extending in the W direction from the negative electrode active material layer 22B. The second portion 222B and the third portion 222C are provided to sandwich the negative electrode covering region 221 in the L direction. The first portion 222A is located near the lower edge 22E3 of the negative electrode 22. The second portion 222B is located near the central axis side edge 22E1 of the negative electrode 22, for example, and the third portion 222C is located near the outer peripheral edge 22E2 of the negative electrode 22. Note that FIGS. 5A and 5B schematically illustrate the negative electrode current collector 22A extending linearly along the W direction. However, in reality, the negative electrode edge 222E of the negative electrode exposed region 222 is bent toward the central axis CL as shown in FIG. 1 and connected to the negative electrode current collector 25. That is, the W direction end of the negative electrode exposed region 222 forms the lower end surface 42 and is connected to the negative electrode current collector 25 (see FIG. 1). The lower end surface 42 is formed by bending the negative electrode edge 222E of the negative electrode exposed region 222 toward the through hole 26 in a wound state.

[0038] In the laminate S20 of the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed therebetween so that the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 face opposite each other along the width direction W. The electrode winding body 20 has the end of the separator 23 fixed by attaching a fixing tape 46 to a side surface portion 45 thereof, thereby preventing loosening of the winding.

[0039] In the secondary battery 1, as shown in FIG. 2 , when the width of the positive electrode exposed region 212 is A and the width of the first portion 222A of the negative electrode exposed region 222 is B, it is preferable that A > B. For example, when the width A = 7 (mm), the width B = 4 (mm). Furthermore, when the width of the portion of the positive electrode exposed region 212 that protrudes from the outer edge of the separator 23 in the width direction is C and the width of the portion of the first portion 222A of the negative electrode exposed region 222 that protrudes from the outer edge on the opposite side in the width direction of the separator 23 is D, it is preferable that C > D. For example, when the width C = 4.5 (mm), the width D = 3 (mm).

[0040] 1 , at the upper part of the secondary battery 1, a plurality of adjacent portions of the positive electrode edge 212E of the positive electrode exposed region 212 wound around the central axis CL in the radial direction (direction R) of the electrode wound body 20 are bent toward the central axis CL so as to overlap with each other, thereby constituting an upper end surface 41 of the electrode wound body 20. Similarly, at the lower part of the secondary battery 1, a plurality of adjacent portions of the negative electrode edge 222E of the negative electrode exposed region 222 wound around the central axis CL in the radial direction (direction R) are bent toward the central axis CL so as to overlap with each other, thereby constituting a lower end surface 42 of the electrode wound body 20. Therefore, a plurality of portions of the positive electrode edge 212E of the positive electrode exposed region 212 are gathered at the upper end surface 41 of the electrode wound body 20, and a plurality of portions of the negative electrode edge 222E of the negative electrode exposed region 222 are gathered at the lower end surface 42 of the electrode wound body 20. To improve contact between the positive electrode edge 212E and the positive electrode current collector 24 for extracting current, multiple portions of the positive electrode edge 212E that are bent toward the central axis CL have flat surfaces. Similarly, to improve contact between the negative electrode edge 222E and the negative electrode current collector 25 for extracting current, multiple portions of the negative electrode edge 222E that are bent toward the central axis CL have flat surfaces. Note that the flat surface referred to here does not only include a completely flat surface, but also includes a surface that has some unevenness or surface roughness to the extent that the positive electrode exposed region 212 and the negative electrode exposed region 222 can be joined to the positive electrode current collector 24 and the negative electrode current collector 25, respectively.

[0041] The positive electrode current collector 21A is made of, for example, aluminum foil, as described below. On the other hand, the negative electrode current collector 22A is made of, for example, copper foil, as described below. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. That is, the Young's modulus of the positive electrode exposed region 212 is lower than that of the negative electrode exposed region 222. Therefore, in one embodiment, it is more preferable that the widths A to D satisfy the relationship A > B and C > D. In this case, when the positive electrode exposed region 212 and the negative electrode exposed region 222 are folded simultaneously from both electrode sides with the same pressure, the heights of the folded portions measured from the tip of the separator 23 may be approximately the same for the positive electrode 21 and the negative electrode 22. At this time, multiple portions of the positive electrode edge portion 212E (FIG. 1) are folded and overlap each other to a moderate extent. This facilitates bonding of the positive electrode exposed region 212 and the positive electrode current collector 24. Similarly, multiple portions of the negative electrode edge portion 222E (FIG. 1) are folded and overlap each other to an appropriate degree, which facilitates joining of the negative electrode exposed region 222 and the negative electrode current collector plate 25. The joining here means joining by, for example, laser welding, but the joining method is not limited to laser welding.

[0042] As shown in FIG. 2 , the portion of the positive electrode exposed region 212 of the positive electrode 21 that faces the negative electrode 22 across the separator 23 is covered with an insulating layer 101. The insulating layer 101 has a width of, for example, 3 mm in the W direction. The insulating layer 101 covers the entire region of the positive electrode exposed region 212 of the positive electrode 21 that faces the negative electrode covering region 221 of the negative electrode 22 via the separator 23. The insulating layer 101 can effectively prevent an internal short circuit in the secondary battery 1, for example, when a foreign object enters between the negative electrode covering region 221 and the positive electrode exposed region 212. Furthermore, when an impact is applied to the secondary battery 1, the insulating layer 101 absorbs the impact and can effectively prevent bending of the positive electrode exposed region 212 and short circuiting between the positive electrode exposed region 212 and the negative electrode 22.

[0043] (Insulating Tapes 53, 54) The secondary battery 1 may further include insulating tapes 53, 54 in the gap between the outer can 11 and the electrode winding body 20. The positive electrode exposed region 212 and the negative electrode exposed region 222, which are concentrated on the upper end surface 41 and the lower end surface 42, are conductors such as bare metal foil. Therefore, if the positive electrode exposed region 212 and the negative electrode exposed region 222 are in close proximity to the outer can 11, a short circuit may occur between the positive electrode 21 and the negative electrode 22 through the outer can 11. Furthermore, if the positive electrode current collector 24 on the upper end surface 41 comes close to the outer can 11, a short circuit may also occur. For this reason, it is preferable to provide insulating tapes 53, 54 as insulating members. The insulating tapes 53, 54 are, for example, adhesive tapes whose base layer is made of one of polypropylene, polyethylene terephthalate, and polyimide and whose base layer has an adhesive layer on one surface. In order to prevent the installation of the insulating tapes 53, 54 from reducing the volume of the electrode winding body 20, the insulating tapes 53, 54 are positioned so as not to overlap with the fixing tape 46 attached to the side portion 45, and the thickness of the insulating tapes 53, 54 is set to be equal to or less than the thickness of the fixing tape 46.

[0044] (Positive Electrode Current Collector 24 and Negative Electrode Current Collector 25) In a typical lithium-ion secondary battery, for example, one lead for current extraction is welded to each of the positive and negative electrodes. However, this increases the internal resistance of the lithium-ion secondary battery and causes the lithium-ion secondary battery to heat up and reach high temperatures during discharge, making it unsuitable for high-rate discharge. Therefore, in the secondary battery 1 of this embodiment, the positive electrode current collector 24 is positioned opposite the upper end face 41 and the negative electrode current collector 25 is positioned opposite the lower end face 42. The positive electrode covering region 211 on the upper end face 41 is welded to the positive electrode current collector 24 at multiple points, and the negative electrode covering region 221 on the lower end face 42 is welded to the negative electrode current collector 25 at multiple points. This reduces the internal resistance of the secondary battery 1. The flat surfaces of the upper end face 41 and the lower end face 42, as described above, also contribute to the low resistance. The positive electrode current collector 24 is located between the battery cover 14 and the upper end face 41. The positive electrode current collector 24 is electrically connected to the battery lid 14 via, for example, a safety valve mechanism 30. The negative electrode current collector 25 is provided between the bottom 11B and the lower end surface 42 of the outer can 11. The negative electrode current collector 25 is electrically connected to, for example, the inner surface of the bottom 11B of the outer can 11. FIG. 6A is a developed view showing an example of the configuration of the positive electrode current collector 24. FIG. 6B is a developed view showing an example of the configuration of the negative electrode current collector 25. The positive electrode current collector 24 is a metal plate made of, for example, aluminum or an aluminum alloy, or a composite material thereof. The negative electrode current collector 25 is a metal plate made of, for example, nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of these.

[0045] As shown in FIG. 6A , the positive current collector 24 has a substantially sector-shaped sector portion 31 and a substantially rectangular strip portion 32. However, the shape of the positive current collector 24 is not limited to the shape shown in FIG. 6A and can be selected arbitrarily. In the secondary battery 1, the positive current collector 24 is housed in the outer can 11 with the strip portion 32 folded relative to the sector portion 31, as shown in FIG. 1 . FIG. 6A shows the positive current collector 24 in an unfolded state. The sector portion 31 is a facing portion that faces and is connected to the upper end surface 41. The sector portion 31 has an outer edge that includes, for example, a straight portion and a curved portion. An opening 35 is formed near the center of the sector portion 31. FIG. 6A illustrates a case in which the opening 35 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction. The strip portion 32 is connected to, for example, a straight portion of the outer edge of the sector portion 31. The strip portion 32 extends in a direction intersecting with the straight portion 31S of the sector portion 31. As shown in Fig. 1 , in the secondary battery 1, the positive electrode current collector plate 24 is provided with the opening 35 overlapping with the through hole 26 in the Z-axis direction. That is, the opening 35 is provided at a position overlapping with a part of the upper end surface 41 on the winding center side in the Z-axis direction. Here, it is preferable that the diameter D35 of the opening 35 is smaller than the diameter D26 of the through hole 26.

[0046] The shaded portion in FIG. 6A is the insulating portion 32A of the strip portion 32. The insulating portion 32A is a portion of the strip portion 32 to which insulating tape is attached or an insulating material is applied. The portion of the strip portion 32 below the insulating portion 32A is a connection portion 32B to the sealing plate, which also serves as an external terminal. The sealing plate is electrically connected to the battery cover 14. Note that, as shown in FIG. 1 , if the secondary battery 1 has a battery structure without a metal center pin in the through hole 26, the strip portion 32 is unlikely to come into contact with a portion of the negative electrode potential. Therefore, the positive electrode current collector 24 may not have the insulating portion 32A. If the positive electrode current collector 24 does not have the insulating portion 32A, the charge / discharge capacity can be increased by increasing the width between the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating portion 32A.

[0047] The shape of the negative electrode current collector 25 shown in FIG. 6B is almost the same as the shape of the positive electrode current collector 24 shown in FIG. 6A . The negative electrode current collector 25 has a substantially sector-shaped fan portion 33 and a substantially rectangular band portion 34. However, the shape of the negative electrode current collector 25 is not limited to the shape shown in FIG. 6B and can be selected arbitrarily. In the secondary battery 1, the negative electrode current collector 25 is housed in the outer can 11 with the band portion 34 folded relative to the fan portion 33, as shown in FIG. 1 . FIG. 6B shows the negative electrode current collector 25 in an unfolded state. The fan portion 33 is a facing portion that faces and is connected to the lower end surface 42. The fan portion 33 has an outer edge that includes, for example, a straight portion and a curved portion. The band portion 34 is connected to, for example, a straight portion 33S of the outer edge of the fan portion 33. The band portion 34 extends in a direction that intersects with the straight portion of the fan portion 33. The strip portion 34 of the negative current collector 25 is shorter than the strip portion 32 of the positive current collector 24 and does not have a portion corresponding to the insulating portion 32A of the positive current collector 24. The strip portion 34 has a plurality of circular protrusions 37 indicated by circles. At least some of the protrusions 37 are welded to the bottom 11B of the outer can 11. During resistance welding, current concentrates on the protrusions 37, melting the protrusions 37 and welding the strip portion 34 to the bottom 11B of the outer can 11. Similar to the positive current collector 24, the negative current collector 25 has an opening 36 formed near the center of the sector-shaped portion 33. In the secondary battery 1, the negative current collector 25 is provided with the opening 36 overlapping the through-hole 26 in the Z-axis direction. FIG. 6B illustrates an example in which the opening 36 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction.

[0048] Due to its planar shape, the sector-shaped portion 31 of the positive current collector 24 covers only a portion of the upper end surface 41. Similarly, due to its planar shape, the sector-shaped portion 33 of the negative current collector 25 covers only a portion of the lower end surface 42. The sector-shaped portions 31 and 33 do not cover the entire upper end surface 41 and the entire lower end surface 42, for example, for the following two reasons. The first reason is to allow the electrolyte to smoothly penetrate into the electrode winding 20, for example, when assembling the secondary battery 1. In particular, in the secondary battery 1 of this embodiment, the positive current collector 24 is provided so that the opening 35 overlaps with a portion of the upper end surface 41 toward the center of the winding in the Z-axis direction. Therefore, a portion of the positive edge portion 212E constituting the upper end surface 41 is not covered by the sector-shaped portion 31 of the positive current collector 24 and is exposed to the opening 35. Therefore, the secondary battery 1 has a structure that allows the electrolyte to penetrate into the electrode winding 20 more quickly. The second reason is to facilitate the release of gas generated when the lithium ion secondary battery is in an abnormally high temperature state or an overcharged state.

[0049] (Positive Electrode Current Collector 21A) The positive electrode current collector 21A contains a conductive material such as aluminum, etc. The positive electrode current collector 21A is, for example, a metal foil made of aluminum or an aluminum alloy.

[0050] (Positive Electrode Active Material Layer 21B) The positive electrode active material layer 21B contains, as the positive electrode active material, one or more positive electrode materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 21B may further contain one or more other materials, such as a positive electrode binder and a positive electrode conductor. The positive electrode material is preferably a lithium-containing compound, more specifically, a lithium-containing composite oxide or a lithium-containing phosphate compound. The lithium-containing composite oxide is an oxide containing lithium and one or more other elements, i.e., elements other than lithium, as constituent elements. The lithium-containing composite oxide has, for example, a layered rock salt type or a spinel type crystal structure. The lithium-containing phosphate compound is a phosphate compound containing lithium and one or more other elements as constituent elements, and has, for example, an olivine type crystal structure. The positive electrode active material layer 21B preferably contains at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide as the positive electrode active material. The positive electrode binder includes, for example, one or more of synthetic rubber and polymer compounds. Examples of synthetic rubber include styrene butadiene rubber, fluorine-based rubber, and ethylene propylene diene. Examples of polymer compounds include polyvinylidene fluoride and polyimide. The positive electrode conductive agent includes, for example, one or more of carbon materials. Examples of carbon materials include graphite, carbon black, acetylene black, and ketjen black. However, the positive electrode conductive agent may also be a metal material or a conductive polymer, as long as it is a conductive material.

[0051] (Negative Electrode Current Collector 22A) The negative electrode current collector 22A contains a conductive material such as copper. The negative electrode current collector 22A is a metal foil made of, for example, nickel, a nickel alloy, copper, or a copper alloy. The surface of the negative electrode current collector 22A is preferably roughened. This is because the so-called anchor effect improves adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A. In this case, it is sufficient that the surface of the negative electrode current collector 22A is roughened at least in the region facing the negative electrode active material layer 22B. The roughening method may be, for example, a method of forming fine particles using an electrolytic process. In the electrolytic process, fine particles are formed on the surface of the negative electrode current collector 22A by electrolysis in an electrolytic bath, resulting in an uneven surface of the negative electrode current collector 22A. Copper foil produced by an electrolytic process is generally called electrolytic copper foil.

[0052] (Negative Electrode Active Material Layer 22B) The negative electrode active material layer 22B contains, as the negative electrode active material, one or more negative electrode materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 22B may further contain one or more other materials, such as a negative electrode binder and a negative electrode conductor. The negative electrode material is, for example, a carbon material. This is because the crystal structure undergoes minimal change upon lithium absorption and desorption, thereby enabling a stable high energy density. Furthermore, the carbon material also functions as a negative electrode conductor, thereby improving the conductivity of the negative electrode active material layer 22B. Examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite. However, the interplanar spacing of the (002) plane of non-graphitizable carbon is preferably 0.37 nm or more. The interplanar spacing of the (002) plane of graphite is preferably 0.34 nm or less. More specifically, the carbon material may be, for example, pyrolytic carbon, cokes, glassy carbon fiber, organic polymer compound calcined bodies, activated carbon, or carbon black. Examples of the cokes include pitch coke, needle coke, and petroleum coke. The organic polymer compound calcined bodies are formed by calcining (carbonizing) polymer compounds such as phenolic resin and furan resin at an appropriate temperature. Alternatively, the carbon material may be low-crystalline carbon heat-treated at temperatures below approximately 1000°C, or amorphous carbon. The carbon material may be fibrous, spherical, granular, or flake-shaped. In the secondary battery 1, when the open-circuit voltage at full charge, i.e., the battery voltage, is 4.25 V or higher, the amount of lithium released per unit mass is greater than when the open-circuit voltage at full charge is 4.20 V, even when the same positive electrode active material is used. Therefore, the amounts of the positive electrode active material and the negative electrode active material are adjusted accordingly. This results in a high energy density.

[0053] The negative electrode active material layer 22B may also contain a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy as the negative electrode active material. A silicon-containing material is a general term for materials containing silicon as a constituent element. However, a silicon-containing material may contain only silicon as a constituent element. The silicon-containing material may be of one type or two or more types. The silicon-containing material is capable of forming an alloy with lithium and may be silicon itself, a silicon alloy, a silicon compound, a mixture of two or more of these, or a material containing one or more of these phases. The silicon-containing material may be crystalline, amorphous, or contain both crystalline and amorphous portions. However, the element described here refers to a general element and may contain trace amounts of impurities. In other words, the purity of the element is not necessarily limited to 100%. Silicon alloys contain, for example, one or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, etc. as constituent elements other than silicon. Silicon compounds contain, for example, one or more of carbon, oxygen, etc. as constituent elements other than silicon. Note that silicon compounds may contain, for example, one or more of the series of constituent elements described for silicon alloys as constituent elements other than silicon. Specifically, silicon alloys and silicon compounds include, for example, SiB 4 , SiB 6 , Mg 2 Si, Ni 2 Si, TiSi 2 , MoSi 2 , CoSi 2 , NiSi 2 , CaSi 2 , CrSi 2 , Cu 5 Si, FeSi 2 , MnSi 2 , NbSi 2 , TaSi 2 , VSi 2 , WSi 2 , ZnSi2 , SiC, Si 3 N 4 , Si 2 N 2 O and SiO v (0<v≦2), etc. However, the range of v can be set arbitrarily, and may be, for example, 0.2<v<1.4.

[0054] (Separator 23) The separator 23 is interposed between the positive electrode 21 and the negative electrode 22. The separator 23 allows lithium ions to pass through while preventing current short-circuiting due to contact between the positive electrode 21 and the negative electrode 22. The separator 23 may be made of one or more types of porous membranes, such as synthetic resins and ceramics, or may be a laminated membrane of two or more types of porous membranes. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene. However, the separator 23 preferably has a substrate made of a single-layer polyolefin porous membrane containing polyethylene. This is because better high-output characteristics can be obtained compared to laminated membranes. When the first separator member 23A and the second separator member constituting the separator 23 are each a single-layer porous membrane made of polyolefin, the thickness of the porous membrane may be, for example, 10 μm or more and 15 μm or less. By making the single-layer porous membrane made of polyolefin 10 μm or more thick, internal short-circuiting can be sufficiently avoided. If the thickness of the single-layer porous film made of polyolefin is 15 μm or less, better discharge capacity characteristics can be obtained. In addition, the surface density of the porous film is, for example, 6.3 g / m ２ 8.3g / m or more ２ The surface density of the single-layer porous film made of polyolefin is preferably 6.3 g / m or less. ２ If the surface density of the single-layer porous film made of polyolefin is 8.3 g / m or more, internal short circuits can be sufficiently avoided. ２ If the content is less than this, better discharge capacity characteristics can be obtained.

[0055] In particular, the separator 23 may include, for example, the porous membrane substrate described above and a polymer compound layer provided on one or both sides of the substrate layer. This is because the adhesion of the separator 23 to each of the positive electrode 21 and the negative electrode 22 is improved, thereby suppressing distortion of the electrode winding body 20. This suppresses the decomposition reaction of the electrolyte and also suppresses leakage of the electrolyte impregnated into the substrate, thereby making it difficult for resistance to increase even with repeated charge and discharge, and suppressing battery swelling. The polymer compound layer includes, for example, a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer compound may be other than polyvinylidene fluoride. To form this polymer compound layer, for example, a solution in which the polymer compound is dissolved in an organic solvent or the like is applied to the substrate, and the substrate is then dried. Alternatively, the substrate may be immersed in the solution and then dried. The polymer compound layer may contain one or more types of insulating particles such as inorganic particles, for example, aluminum oxide and aluminum nitride.

[0056] (Electrolyte) The electrolyte contains a solvent and an electrolyte salt. However, the electrolyte may further contain one or more other materials, such as additives. The solvent contains one or more non-aqueous solvents, such as organic solvents. An electrolyte containing a non-aqueous solvent is a so-called non-aqueous electrolyte. The non-aqueous solvent contains, for example, a fluorine compound and a dinitrile compound. The fluorine compound may include, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid ester, and fluorinated ether. The non-aqueous solvent may also contain at least one nitrile compound other than the dinitrile compound, such as a mononitrile compound or a trinitrile compound. The dinitrile compound is preferably succinonitrile (SN). However, the dinitrile compound is not limited to succinonitrile and may be other dinitrile compounds, such as adiponitrile.

[0057] The electrolyte salt may include one or more salts, such as lithium salts. However, the electrolyte salt may also include salts other than lithium salts, such as salts of light metals other than lithium. Examples of lithium salts include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium tetraphenylborate (LiB(C(H)), lithium methanesulfonate (LiCHSO), lithium trifluoromethanesulfonate (LiCFSO), lithium tetrachloroaluminate (LiAlCl), dilithium hexafluorosilicate (LiSiF), lithium chloride (LiCl), and lithium bromide (LiBr). Among these, one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate are preferred, with lithium hexafluorophosphate being more preferred. The content of the electrolyte salt is not particularly limited, but is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent. When the electrolyte solution contains LiPF as the electrolyte salt, ６ When the electrolyte contains LiPF ６ The concentration of the electrolyte salt is preferably 1.25 mol / kg or more and 1.45 mol / kg or less. This is because it is possible to prevent cycle deterioration due to salt consumption (decomposition) during high-load rate charging, thereby improving high-load cycle characteristics. ６ In addition to LiBF ４ When further containing LiBF in the electrolyte ４ The concentration of salt is preferably 0.001 (wt %) or more and 0.1 (wt %) or less, because this more effectively prevents cycle deterioration due to salt consumption (decomposition) during high-load rate charging, thereby further improving high-load cycle characteristics.

[0058] [1-2. Operation] In the secondary battery 1 of this embodiment, for example, during charging, lithium ions are released from the positive electrode 21 and are absorbed into the negative electrode 22 via the electrolyte. In addition, in the secondary battery 1, for example, during discharging, lithium ions are released from the negative electrode 22 and are absorbed into the positive electrode 21 via the electrolyte.

[0059] 1-3. Manufacturing Method] A method for manufacturing the secondary battery 1 will be described with reference to Fig. 7 in addition to Fig. 1 to Fig. 6B. Fig. 7 is a perspective view illustrating the manufacturing process of the secondary battery shown in Fig. 1.

[0060] First, a positive electrode current collector 21A is prepared, and a positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A. Then, an insulating layer 101 is formed on the surface of the positive electrode current collector 21A along a first edge 21BT1 of the positive electrode active material layer 21B. Furthermore, predetermined regions of the positive electrode active material layer 21B are dug down by, for example, laser ablation, to form thin-walled portions 61. Through these operations, the positive electrode 21 is obtained. Next, a negative electrode current collector 22A is prepared, and a negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A, thereby forming a negative electrode 22 having a negative electrode covering region 221 and a negative electrode exposed region 222. A drying process may be performed on the positive electrode 21 and the negative electrode 22. Next, the positive electrode 21 and the negative electrode 22 are stacked with the first separator member 23A and the second separator member 23B interposed therebetween so that the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are opposite each other in the W direction, thereby producing a laminate S20. The laminate S20 is then spirally wound so as to form through-holes 26. For example, a cylindrical winding core is used as a jig, and the laminate S20 is wound around the cylindrical winding core. Furthermore, a fixing tape 46 is attached to the outermost periphery of the spirally wound laminate S20, and the winding core is then removed. This results in an electrode winding body 20, as shown in FIG. 7A .

[0061] Next, as shown in Fig. 7B , the edge of a flat plate having a thickness of, for example, 0.5 mm is pressed perpendicularly against the upper end surface 41 and the lower end surface 42 of the electrode winding body 20, i.e., in the Z-axis direction, thereby locally bending a portion of the upper end surface 41 and a portion of the lower end surface 42. As a result, grooves 43 are formed extending radially from the through-holes 26 in the radial direction (direction R). Note that the number and arrangement of grooves 43 shown in Fig. 7B are merely examples and the present disclosure is not limited thereto.

[0062] Next, as shown in FIG. 7C , substantially the same pressure is applied substantially simultaneously from above and below the electrode winding 20 to the upper end face 41 and the lower end face 42 in a direction approximately perpendicular to the electrode winding 20. At this time, a rod-shaped jig, for example, is inserted into the through-hole 26. This bends the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222, respectively, so that the upper end face 41 and the lower end face 42 each become flat. At this time, it is preferable that adjacent portions of the positive electrode edge 212E of the positive electrode exposed region 212 on the upper end face 41 in the radial direction of the electrode winding 20 bend toward the through-hole 26 so as to overlap each other. Similarly, it is preferable that adjacent portions of the negative electrode edge 222E of the negative electrode exposed region 222 on the lower end face 42 in the radial direction of the electrode winding 20 bend toward the through-hole 26 so as to overlap each other. Thereafter, the sectorial portion 31 of the positive current collector plate 24 is joined to the upper end face 41 by laser welding or the like, and the sectorial portion 33 of the negative current collector plate 25 is joined to the lower end face 42 by laser welding or the like.

[0063] Next, insulating tapes 53 and 54 are attached to predetermined positions of the electrode winding body 20. Thereafter, as shown in Fig. 7D, the strip portion 32 of the positive current collector plate 24 is bent and inserted into the hole 12H of the insulating plate 12. Also, the strip portion 34 of the negative current collector plate 25 is bent and inserted into the hole 13H of the insulating plate 13.

[0064] Next, the electrode winding body 20 assembled as described above is inserted into the outer can 11 shown in Figure 7(E), and the bottom 11B of the outer can 11 is welded to the negative electrode current collector 25. After that, a constricted portion 11S is formed near the open end 11N of the outer can 11. Furthermore, after the electrolyte is poured into the outer can 11, the strip portion 32 of the positive electrode current collector 24 is welded to the safety valve mechanism 30.

[0065] 7(F), the outer can 11 is sealed using the gasket 15, the safety valve mechanism 30, and the battery lid 14, utilizing the constricted portion 11S. Finally, the outer can 11, with the washer 55 attached to the battery lid 14, is covered with the outer tube 50, and the outer tube 50 is heated and shrunk by applying hot air to the outer tube 50, for example, and the outer tube 50 is then tightly attached to the outer surface of the outer can 11.

[0066] In this way, the secondary battery 1 of this embodiment is completed.

[0067] <B. Application Examples> The applications of the secondary battery 1 according to the embodiment of the present disclosure described above are as follows, for example.

[0068] 8 is a block diagram showing an example of a circuit configuration when a battery according to an embodiment of the present invention (hereinafter referred to as a secondary battery) is applied to a battery pack 300. The battery pack 300 includes a battery pack 301, an exterior body 305, a switch unit 304 having a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

[0069] The battery pack 300 includes a positive terminal 321 and a negative terminal 322. When charging, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of a charger, respectively, for charging. When using the electronic device, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of the electronic device, respectively, for discharging.

[0070] The battery pack 301 is formed by connecting a plurality of secondary batteries 301a in series or parallel. The secondary batteries 301a can be the secondary batteries 1 described above. While Fig. 8 shows an example in which six secondary batteries 301a are connected in a 2-parallel-3-series (2P3S) configuration, any other connection method may be used, such as n-parallel or m-series (n and m are integers).

[0071] The switch unit 304 includes a charge control switch 302a and a diode 302b, as well as a discharge control switch 303a and a diode 303b, and is controlled by the control unit 310. The diode 302b has a polarity opposite to the charge current flowing from the positive terminal 321 to the battery pack 301, and a polarity forward to the discharge current flowing from the negative terminal 322 to the battery pack 301. The diode 303b has a polarity forward to the charge current and opposite to the polarity of the discharge current. Although the switch unit 304 is provided on the + side in FIG. 8, it may also be provided on the - side.

[0072] The charge control switch 302a is controlled by the charge / discharge control unit so that it is turned off when the battery voltage reaches the overcharge detection voltage and so that no charging current flows in the current path of the battery pack 301. After the charge control switch 302a is turned off, only discharging is possible via the diode 302b. Furthermore, the control unit 310 controls the switch so that it is turned off when a large current flows during charging and so that the charging current flows in the current path of the battery pack 301. The discharge control switch 303a is controlled by the control unit 310 so that it is turned off when the battery voltage reaches the overdischarge detection voltage and so that no discharging current flows in the current path of the battery pack 301. After the discharge control switch 303a is turned off, only charging is possible via the diode 303b. Furthermore, the control unit 310 controls the switch so that it is turned off when a large current flows during discharging and so that the discharging current flows in the current path of the battery pack 301.

[0073] The temperature detection element 308 is, for example, a thermistor, and is provided near the battery pack 301. It measures the temperature of the battery pack 301 and supplies the measured temperature data to the control unit 310. The voltage detection unit 311 measures the voltage of the battery pack 301 and each of the secondary batteries 301a that make up the battery pack 301, A / D converts this measured voltage data, and supplies it to the control unit 310. The current measurement unit 313 measures the current using the current detection resistor 307, and supplies this measured current data to the control unit 310. The switch control unit 314 controls the charge control switch 302a and the discharge control switch 303a of the switch unit 304 based on the voltage data and current data input from the voltage detection unit 311 and the current measurement unit 313.

[0074] When the voltage of any of the multiple secondary batteries 301a falls below the overcharge detection voltage or the overdischarge detection voltage, or when a large current suddenly flows, the switch control unit 314 sends a control signal to the switch unit 304 to prevent overcharging, overdischarging, and overcurrent charging / discharging. Here, for example, if the secondary battery is a lithium-ion secondary battery, the overcharge detection voltage is set to, for example, 4.20 V±0.05 V, and the overdischarge detection voltage is set to, for example, 2.4 V±0.1 V.

[0075] The charge / discharge control switch can be a semiconductor switch such as a MOSFET. In this case, the parasitic diode of the MOSFET functions as diodes 302b and 303b. When a P-channel FET is used as the charge / discharge control switch, switch control unit 314 supplies control signals DO and CO to the gates of charge control switch 302a and discharge control switch 303a, respectively. When charge control switch 302a and discharge control switch 303a are P-channel, they are turned ON by a gate potential that is lower than the source potential by a predetermined value or more. That is, during normal charge and discharge operations, control signals CO and DO are set to a low level, and charge control switch 302a and discharge control switch 303a are turned ON.

[0076] For example, in the event of overcharging or overdischarging, the control signals CO and DO are set to high level, and the charge control switch 302a and the discharge control switch 303a are set to the OFF state.

[0077] The memory 317 is made up of RAM or ROM, such as a non-volatile memory such as an erasable programmable read-only memory (EPROM). Numerical values ​​calculated by the control unit 310 and the internal resistance values ​​of the secondary batteries 301a in their initial states measured during the manufacturing process are stored in advance in the memory 317, and the memory 317 can be rewritten as needed. Furthermore, by storing the full charge capacity of the secondary batteries 301a in the memory 317, the remaining capacity can be calculated together with the control unit 310.

[0078] The temperature detection unit 318 measures the temperature using the temperature detection element 308, and controls charging and discharging when abnormal heat is generated, and corrects the calculation of the remaining capacity.

[0079] [B-2. Power Storage System] The secondary battery according to the embodiment of the present disclosure described above can be mounted on devices such as electronic devices, electric vehicles, electric aircraft, and power storage devices, or can be used to supply power.

[0080] Examples of electronic devices include notebook computers, smartphones, tablet devices, PDAs (personal digital assistants) as portable information terminals, mobile phones, wearable devices, cordless phone handsets, video movie players, digital still cameras, e-books, electronic dictionaries, music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric shavers, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical equipment, robots, road conditioners, and traffic lights.

[0081] Examples of electric vehicles include railcars, golf carts, electric carts, electric vehicles (including hybrid vehicles), and the like, and the device is used as a driving power source or auxiliary power source for these. Examples of power storage devices include power storage power sources for buildings such as homes, or for power generation facilities.

[0082] <C. Specifics> (1-1) [Configuration] A positive electrode active material layer of a positive electrode of embodiment 1-1 that can be applied to batteries such as lithium-ion secondary batteries has a positive electrode active material formed by adhering Zr (zirconium) or Ti (titanium) to the surfaces of positive electrode active material particles containing lithium nickel cobalt aluminum oxide (NCA) having a Ni ratio of 85% or more or nickel cobalt manganese oxide (NCM) having a Ni ratio of 85% or more. In this positive electrode active material, the concentration of Zr or Ti is relatively high near the surfaces of the positive electrode active material particles and relatively low inside the positive electrode active material particles.

[0083] The positive electrode active material of the positive electrode of embodiment 1-1 that can be applied to batteries such as lithium ion secondary batteries is, for example, LiNiO 2 , LiNi 0.9 Co 0.1 O 2 , LiNi 0.85 Co 0.1 Al 0.05 O 2 , LiNi 0.90 Co 0.05 Al 0.05 O 2 , LiNi 0.82 Co 0.14 Al 0.04 O 2 , LiNi 0.78 Co 0.18 Al 0.04 O 2 and LiNi 0.90 Co 0.06 Al 0.04 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.9 Co 0.05 Mn 0.05 O 2 , LiNi 0.3 Co 0.3 Mn 0.3 O 2 and LiNi 0.84 Co 0.08 Mn 0.08O 2 , LiNi 0.80 Co 0.10 Mn 0.05 Al 0.05 O 2 The positive electrode active material is a lithium-nickel composite oxide such as a lithium-nickel composite oxide (B), whose surface is coated with a boron compound. In other words, the positive electrode active material (positive electrode material) contains a lithium-nickel composite oxide and a boron compound that coats the surface of the lithium-nickel composite oxide. The boron compound is a general term for compounds containing boron (B) as a constituent element. This is because the surface of the lithium-nickel composite oxide is electrochemically stabilized, thereby suppressing the decomposition reaction of the electrolyte on the surface of the lithium-nickel composite oxide. The type of boron compound is not particularly limited, but examples include boric acid (H3BO3), lithium tetraborate (Li2BO7), ammonium pentaborate (NH4BO8), lithium metaborate (LiBO2), and boron oxide (BO3).

[0084] (1-2) [Configuration] Figure 9A is a cross-sectional schematic diagram showing the configuration of a portion of a positive electrode 21 of embodiment 1-2 that can be applied to a battery such as a lithium-ion secondary battery. As shown in Figure 9A, in the positive electrode 21 of embodiment 1-2, the positive electrode active material layer 21B has a plurality of particles 21B-1 having a relatively large diameter and a plurality of particles 21B-2 having a relatively small diameter. Coatings 21CL1 and 21CL2 containing boric acid are provided on the surfaces of the particles 21B-1 and 21B-2, respectively. Note that the coatings 21CL1 and 21CL2 only need to cover at least a portion of the surface of the particles 21B-1 and at least a portion of the surface of the particles 21B-2. Here, it is preferable that the coating mass (weight) per unit surface area of ​​the coating 21CL2 covering the surface of the particles 21B-2 is greater than the coating mass (weight) per unit surface area of ​​the coating 21CL1 covering the surface of the particles 21B-1.

[0085] [Effect] According to the positive electrode 21 of aspect 1-2, by selectively coating a large amount of boric acid on the small-diameter particles 21B-2, which are relatively susceptible to deterioration, deterioration of the positive electrode active material can be suppressed and reaction resistance can be reduced.

[0086] (1-3) [Configuration] FIG. 9B is a cross-sectional schematic diagram illustrating the configuration of a portion of a positive electrode 21 according to embodiment 1-3, which can be used in a battery such as a lithium-ion secondary battery. As shown in FIG. 9B, in the positive electrode 21 according to embodiment 1-3, the positive electrode active material layer 21B includes a plurality of particles 21B-1 having a relatively large diameter and a plurality of particles 21B-2 having a relatively small diameter. Coatings 21CL1 and 21CL2 containing boric acid are provided on the surfaces of the particles 21B-1 and 21B-2, respectively. It is sufficient that the coatings 21CL1 and 21CL2 cover at least a portion of the surface of the particles 21B-1 and at least a portion of the surface of the particles 21B-2. However, the coatings 21CL1 and 21CL2 are not present in the first layer region of the positive electrode active material layer 21B, which is located closest to the positive electrode current collector 21A. Furthermore, the deposition mass of coatings 21CL1 and 21CL2 in the nth layer region of positive electrode active material layer 21B, which is located farthest from positive electrode current collector 21A, i.e., closest to separator 23, is greater than the deposition mass of coatings 21CL1 and 21CL2 in the region between the first layer and the nth layer. The deposition mass here refers to the weight per unit surface area of ​​coating 21CL1 covering the surface of particle 21B-1, or the weight per unit surface area of ​​coating 21CL2 covering the surface of particle 21B-2.

[0087] [Effect] In the nth layer of the positive electrode active material layer 21B, which is located closest to the separator 23, Li ions diffuse rapidly, and deterioration of the positive electrode active material tends to progress. According to the positive electrode 21 of Aspect 1-5, the amount of the boric acid-containing coating 21CL1, 21CL2 attached to the nth layer, which is located closest to the separator 23, is made larger than that of the other layers, thereby suppressing deterioration of the positive electrode active material. Therefore, according to the positive electrode 21 of Aspect 1-3, it is possible to suppress deterioration in reaction resistance after charge-discharge cycles in the nth layer region, which is located closest to the separator 23, of the positive electrode active material layer 21B, while suppressing an increase in reaction resistance in the first layer region, which is located closest to the positive electrode current collector 21A of the positive electrode active material layer 21B.

[0088] 9C is a schematic cross-sectional view showing an enlarged view of cathode active material particles 21B-1 and 21B-2 included in cathode active material layer 21B of embodiment 1-4, which can be used in batteries such as lithium-ion secondary batteries. As shown in FIG. 9C, cathode active material layer 21B of embodiment 1-4 includes a mixture of cathode active material particles 21B-1 coated with binder 21BD and cathode active material particles 21B-2 not coated with binder 21BD.

[0089] [Effects] The positive electrode active material layer 21B of aspect 1-4 is expected to achieve high output. For example, the binder 21BD is maintained at the contact points between the positive electrode active material particles 21B-1 and the positive electrode active material particles 21B-2. That is, the mechanical strength of the positive electrode active material layer 21B is maintained. Meanwhile, the presence of the positive electrode active material particles 21B-2 that are not coated with the binder 21BD enables good occlusion and release of lithium ions.

[0090] (2-1) [Configuration] Fig. 10A is a cross-sectional schematic diagram showing the configuration of a portion of a positive electrode 21 according to embodiment 2-1-1, which can be used in a battery such as a lithium-ion secondary battery. As shown in Fig. 10A, in the positive electrode 21 according to embodiment 2-1-1, the positive electrode active material layer 21B contains positive electrode active material particles 21B-1 made of lithium nickel cobalt aluminum oxide (NCA) or the like, carbon nanotubes (CNT), and acetylene black AB. The acetylene black AB is present near the interface between the positive electrode current collector 21A and the positive electrode active material layer 21B.

[0091] 10B is a cross-sectional schematic diagram showing the configuration of a portion of the positive electrode 21 of Embodiment 2-1-2 that can be applied to a battery such as a lithium-ion secondary battery. The configuration of the positive electrode 21 of Embodiment 2-1-2 is substantially the same as the configuration of the positive electrode 21 of Embodiment 2-1-1, except that acetylene black AB is not included.

[0092] 10C is a cross-sectional schematic diagram illustrating the configuration of a portion of a positive electrode 21 of Aspect 2-1-3 that can be used in a battery such as a lithium-ion secondary battery. The configuration of the positive electrode 21 of Aspect 2-1-3 is substantially the same as the configuration of the positive electrode 21 of Aspect 2-1-1, except that it does not contain carbon nanotubes (CNT) and that acetylene black AB is dispersed in portions of the positive electrode active material layer 21B other than near the interface between the positive electrode current collector 21A and the positive electrode active material layer 21B.

[0093] 10D is a cross-sectional schematic diagram illustrating the configuration of a portion of a positive electrode 21 of Embodiment 2-1-4 that can be used in a battery such as a lithium-ion secondary battery. The configuration of the positive electrode 21 of Embodiment 2-1-4 is substantially the same as the configuration of the positive electrode 21 of Embodiment 2-1-1, except that acetylene black AB is dispersed and present in portions of the positive electrode active material layer 21B other than near the interface between the positive electrode current collector 21A and the positive electrode active material layer 21B.

[0094] [Effects] Compared with the positive electrode active material layers 21B of Aspect 2-1-2 to Aspect 2-1-4, the positive electrode active material layer 21B of Aspect 2-1-1 can achieve both a reduced composite resistance (resistance inside the positive electrode active material layer 21B) and a reduced interface resistance (resistance at the interface between the positive electrode current collector 21A and the positive electrode active material layer 21B), and can also obtain excellent load characteristics. This is thought to be because the dispersion of carbon nanotubes (CNT) throughout the positive electrode active material layer 21B ensures a diffusion path for Li ions, and the provision of acetylene black (AB) near the interface between the positive electrode current collector 21A and the positive electrode active material layer 21B can form a good electron path.

[0095] (2-2) [Configuration] Figure 11A is a cross-sectional schematic diagram showing the configuration of a portion of a positive electrode 21 of embodiment 2-2-1 that can be applied to a battery such as a lithium-ion secondary battery. As shown in Figure 11A, in the positive electrode 21 of embodiment 2-2-1, the positive electrode active material layer 21B includes positive electrode active material particles 21B-1 and 21B-2 made of lithium nickel cobalt aluminum oxide (NCA) or the like, carbon nanotubes (CNT) having a length of approximately 150 μm, and acetylene black AB. The acetylene black AB is present, for example, between a plurality of positive electrode active material particles 21B-1 and 21B-2. In the positive electrode 21 of embodiment 2-2-1, the positive electrode active material layer 21B includes a plurality of particles 21B-1 having a relatively large diameter and a plurality of particles 21B-2 having a relatively small diameter.

[0096] 11B is a cross-sectional schematic diagram showing the configuration of a portion of the positive electrode 21 of Embodiment 2-2-2 that can be applied to a battery such as a lithium ion secondary battery. The configuration of the positive electrode 21 of Embodiment 2-2-2 is substantially the same as the configuration of the positive electrode 21 of Embodiment 2-2-1, except that the length of the carbon nanotubes CNT is 50 μm or less.

[0097] [Effects] According to the positive electrode 21 of Aspect 2-2-1, the positive electrode active material layer 21B contains carbon nanotubes CNT that are longer than the positive electrode 21 of Aspect 2-2-2. This reduces the variation in electronic resistance in the positive electrode active material layer 21B, making it possible to prevent isolation of the electron path of positive electrode active material particles, particularly those with a relatively small particle diameter, and to mitigate deterioration due to repeated charge and discharge.

[0098] (2-3) [Configuration] Figure 12A is a cross-sectional schematic diagram illustrating the configuration of a portion of a cathode active material layer 21B according to aspect 2-3-1, which may be used in a battery such as a lithium-ion secondary battery. As shown in Figure 12A, the cathode active material layer 21B according to aspect 2-3-1 includes a plurality of cathode active material particles 21B-1, acetylene black AB, which is a spherical conductive additive, and carbon nanotubes (CNT), which are linear conductive additives. The carbon nanotubes (CNT) may be uniformly distributed throughout the cathode active material layer 21B by mixing a CNT dispersion liquid in which the CNTs are uniformly dispersed with a cathode mixture slurry during the fabrication process of the cathode active material layer 21B and applying the mixture to the cathode current collector 21A. The carbon nanotubes (CNT) may have a length of, for example, 100 μm or more. Carbon nanotubes CNT can be detected by diluting the positive electrode active material layer 21B with NMP (N-methyl-2-pyrrolidone), drying it, and observing the resultant with an SEM.

[0099] 12A is a cross-sectional schematic diagram illustrating the configuration of a portion of a cathode active material layer 21B according to Embodiment 2-3-2, which can be used in a battery such as a lithium-ion secondary battery. The configuration of the cathode 21 according to Embodiment 2-3-2 is substantially the same as the configuration of the cathode active material layer 21B according to Embodiment 2-3-1, except that it does not contain carbon nanotubes (CNT).

[0100] [Effects] Compared to the positive electrode active material layer 21B of embodiment 2-3-2, the positive electrode active material layer 21B of embodiment 2-3-1 contains both carbon nanotubes (CNT) and acetylene black (AB), which prevents isolation of the electron path of the positive electrode active material in the positive electrode active material layer 21B and reduces variations in the internal resistance of the positive electrode active material layer 21B. Furthermore, since the positive electrode active material layer 21B contains carbon nanotubes (CNT) in addition to acetylene black (AB), the total amount of acetylene black (AB) contained in the positive electrode active material layer 21B can be reduced. This facilitates the migration of Li ions.

[0101] (2-4) [Configuration] FIG. 13 is a cross-sectional schematic diagram illustrating the configuration of a portion of a cathode active material layer 21B according to embodiment 2-4, which may be applied to a battery such as a lithium-ion secondary battery. As shown in FIG. 13, the cathode active material layer 21B according to embodiment 2-4 includes a plurality of cathode active material particles 21B-1, acetylene black AB as a spherical conductive additive, carbon nanotubes CNT as a linear conductive additive, and a conductive bridge BG. The bridge BG connects adjacent cathode active material particles 21B-1. The bridge BG may be, for example, aluminum (Al) powder, aluminum flakes, or aluminum fibers. Alternatively, the bridge BG may be formed by coating the surface of aluminum (Al) powder, aluminum flakes, or aluminum fibers with a fluorine compound. As a constituent material of the bridge BG, a metal that does not decompose even at high potential may be used in addition to aluminum.

[0102] [Effects] According to the cathode active material layer 21B of aspect 2-4, the plurality of cathode active material particles 21B-1 are connected by the bridges BG. Therefore, compared with the cathode active material layer 21B of an aspect not including the bridges BG, the bonds between the cathode active material particles 21B-1 are strengthened, and the mechanical strength of the cathode active material layer 21B can be increased. In addition, isolation of the cathode active material is reduced, and deterioration in load characteristics can be suppressed even when the cathode active material layer 21B is made thicker.

[0103] (2-5) [Configuration] The positive electrode current collector 21A of the positive electrode 21 of embodiment 2-5, which can be used in batteries such as lithium-ion secondary batteries, is made of an Al material having a total mass purity of Si (silicon) and Fe (iron) of 0.05% or less, a mass purity of Cu (copper) of 0.1% or less, a mass purity of Mg (magnesium) of 0.1% or less, and a total mass purity of other elements excluding the above elements of 0.05% or less. Furthermore, the Al material constituting the positive electrode current collector 21A of embodiment 2-5 has a thermal conductivity of 238 W / m C or more and a thermal conductivity of 70 kN / mm ２ It has a longitudinal elastic modulus of at least 1000.

[0104] [Effects] The positive electrode current collector 21A of aspect 2-5 uses aluminum foil with high thermal conductivity (few impurities). This improves the heat dissipation performance of the electrode winding body 20. That is, heat generated inside the battery is efficiently dissipated to the outside. This suppresses temperature increases in the electrode material and electrolyte. Furthermore, suppressing increases in internal resistance improves the energy supply from the battery and the charge / discharge rate, leading to higher output. Furthermore, improved heat dissipation performance suppresses temperature increases, reducing excessive temperature increases and thermal stress in the electrode winding body 20 and maintaining a stable operating state.

[0105] (2-6) [Configuration] FIG. 14 is a cross-sectional schematic diagram illustrating the configuration of a positive electrode current collector 21A according to embodiment 2-6 that can be used in batteries such as lithium-ion secondary batteries. As shown in FIG. 14, in the positive electrode current collector 21A according to embodiment 2-6, the front surface 21AS1 and the back surface 21AS2 each have an uneven shape. Note that the shapes of the front surface 21AS1 and the back surface 21AS2 shown in FIG. 14 are merely examples, and the present disclosure is not limited thereto. Furthermore, when the positive electrode active material layer 21B is formed only on the front surface 21AS1, the back surface 21AS2 does not need to have an uneven shape. The uneven shapes of the front surface 21AS1 and the back surface 21AS2 are formed, for example, by edging.

[0106] [Effects] According to the positive electrode current collector 21A of aspect 2-6, the front surface 21AS1 and the back surface 21AS2 each have an uneven shape, which increases the surface area of ​​the front surface 21AS1 and the back surface 21AS2. This increases the contact area at the interface between the positive electrode current collector 21A and the positive electrode active material layer 21B, thereby reducing the resistance at the interface between the positive electrode current collector 21A and the positive electrode active material layer 21B. Furthermore, the uneven shape provides an anchor effect that holds the positive electrode active material layer 21B in place, thereby preventing the positive electrode active material layer 21B from falling off or peeling off from the positive electrode current collector 21A.

[0107] 15 is an enlarged cross-sectional view showing a partial configuration of a positive electrode 21 according to embodiment 3-1 that can be used in a battery such as a lithium-ion secondary battery. As shown in FIG. 15, the positive electrode 21 according to embodiment 3-1 includes a positive electrode current collector 21A, a positive electrode active material layer 21B, an undercoat layer 21C, and a masking layer 21D.

[0108] The positive electrode current collector 21A contains a conductive material such as aluminum. The positive electrode current collector 21A is a metal foil made of aluminum or an aluminum alloy. The ends of the positive electrode current collector 21A in the width direction (W direction) are exposed and are not covered by the positive electrode active material layer 21B, the undercoat layer 21C, or the masking layer 21D.

[0109] The undercoat layer 21C is made of, for example, carbon black or carbon nanotubes (CNTs). The undercoat layer 21C covers both surfaces of the positive electrode current collector 21A. However, the undercoat layer 21C does not reach the tip T21A of the positive electrode current collector 21A. That is, in the W direction, the position of the tip T21C of the undercoat layer 21C is set back inward from the position of the tip T21A of the positive electrode current collector 21A.

[0110] The positive electrode active material layer 21B is provided on the undercoat layer 21C. However, the positive electrode active material layer 21B does not reach the tip T21C of the undercoat layer 21C. That is, in the W direction, the position of the tip T21B of the positive electrode active material layer 21B is set back more inward than the position of the tip T21C of the undercoat layer 21C. Therefore, the vicinity of the tip T21C of the undercoat layer 21C is not covered by the positive electrode active material layer 21B. In the positive electrode 21 of aspect 3-1, the vicinity of the boundary between the undercoat layer 21C and the positive electrode active material layer 21B is covered by the masking layer 21D. However, the undercoat layer 21C and the positive electrode active material layer 21B each include a portion not covered by the masking layer 21D. The masking layer 21D can be made of an insulating material, such as a resin containing modified PVDF (polyvinylidene fluoride) or copolymer PVDF.

[0111] [Effects] In the positive electrode 21 of aspect 3-1, the undercoat layer 21C is provided, thereby reducing electrical resistance and suppressing heat generation during high-load charge / discharge. Furthermore, the undercoat layer 21C improves heat dissipation and suppresses heat generation during high-load charge / discharge. Furthermore, because a portion of the undercoat layer 21C is covered with the masking layer 21D, even if the positive electrode active material layer 21B is thick, detachment of the positive electrode active material layer 21B from the positive electrode current collector 21A due to differences in hardness between the positive electrode active material layer 21B and the masking layer 21D is avoided.

[0112] (3-2) [Configuration] In the cathode 21 of aspect 3-2, which can be applied to batteries such as lithium-ion secondary batteries, the undercoat layer 21C is composed of an organic compound such as non-fibrous conductive carbon, fibrous carbon, or particulate carbon, or an inorganic compound such as a silicate compound or aluminum hydrate oxide. For example, when the undercoat layer 21C is applied to the surface of a cathode current collector 21A such as aluminum foil, or when the undercoat layer is applied to the surface of the cathode current collector 21A and then baked, and the image captured by a CCD image sensor while irradiated with an LED light source of 1,400,000 lx, is binarized, the luminance value of the undercoat layer 21C is 230 or less. The color of the undercoat layer 21C is not specified, but it is preferable that the RGB color is (i, i, i) where i = 0 to 230.

[0113] [Effect] In the positive electrode 21 of aspect 3-2, for example, the boundary position between the region where the undercoat layer 21C is applied and the region where the masking layer 21D is applied as an upper layer of the undercoat layer 21C can be detected more accurately.

[0114] 16A is an enlarged cross-sectional view showing a partial configuration of a positive electrode 21 according to embodiment 4-1, which may be used in a battery such as a lithium-ion secondary battery. As shown in FIG. 16A, the positive electrode 21 according to embodiment 4-1 includes a positive electrode current collector 21A, a positive electrode active material layer 21B, an undercoat layer 21C, and a masking layer 21D.

[0115] The positive electrode current collector 21A includes a conductive material such as aluminum. The positive electrode current collector 21A is a metal foil made of aluminum or an aluminum alloy. The positive electrode current collector 21A has a first end 21A1 in the width direction (W direction) bent.

[0116] The undercoat layer 21C is made of, for example, carbon black or carbon nanotubes (CNTs). The undercoat layer 21C covers both surfaces of the positive electrode current collector 21A. However, the undercoat layer 21C does not reach the tip T21A of the first end 21A1 of the positive electrode current collector 21A. That is, in the W direction, the position of the tip T21C of the undercoat layer 21C is set back further inward than the position of the tip T21A of the positive electrode current collector 21A. Therefore, the vicinity of the tip T21A of the first end 21A1 of the positive electrode current collector 21A is exposed and not covered by the undercoat layer 21C.

[0117] The positive electrode active material layer 21B is provided on the undercoat layer 21C. However, the positive electrode active material layer 21B does not reach the tip T21C of the undercoat layer 21C. That is, in the W direction, the position of the tip T21B of the positive electrode active material layer 21B is set back more inward than the position of the tip T21C of the undercoat layer 21C. Therefore, the vicinity of the tip T21C of the undercoat layer 21C is not covered by the positive electrode active material layer 21B. In the positive electrode 21 of aspect 4-1, the vicinity of the boundary between the undercoat layer 21C and the positive electrode active material layer 21B is covered by the masking layer 21D. However, the undercoat layer 21C and the positive electrode active material layer 21B each include a portion not covered by the masking layer 21D. The masking layer 21D can be made of an insulating material, such as a resin containing modified PVDF (polyvinylidene fluoride) or copolymer PVDF.

[0118] [Effects] In the positive electrode 21 of embodiment 4-1, the undercoat layer 21C is provided, which reduces electrical resistance and suppresses heat generation during high-load charge / discharge. The undercoat layer 21C also improves heat dissipation and suppresses heat generation during high-load charge / discharge. Furthermore, the undercoat layer 21C covers a portion of the bent first end 21A1 of the positive current collector 21A, which improves heat diffusion at the welded portion between the positive current collector 21A and the positive current collector plate 24.

[0119] (4-2) [Configuration] Figure 16B is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 of embodiment 4-2 that can be used in a battery such as a lithium-ion secondary battery. As shown in Figure 16B, in the positive electrode 21 of embodiment 4-2, the position of the tip T21C of the undercoat layer 21C is recessed inward from the bending position T21A1 of the first end 21A1 of the positive electrode current collector 21A. Except for this point, the configuration of the positive electrode 21 of embodiment 4-2 is substantially the same as the configuration of the positive electrode 21 of embodiment 4-1 shown in Figure 16A.

[0120] [Effect] In the positive electrode 21 of aspect 4-2, the provision of the undercoat layer 21C improves heat dissipation, while preventing the undercoat layer 21C from peeling off when the first end 21A1 of the positive electrode current collector 21A and the positive electrode current collector plate 24 are welded together.

[0121] (4-3) [Configuration] Figure 16C is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 of embodiment 4-3 that can be used in a battery such as a lithium-ion secondary battery. As shown in Figure 16C, in the positive electrode 21 of embodiment 4-3, the position of the tip T21C of the undercoat layer 21C is recessed further inward than the tip T21D of the masking layer 21D. Therefore, the undercoat layer 21C is covered by the masking layer 21D and the positive electrode active material layer 21B. Except for this point, the configuration of the positive electrode 21 of embodiment 4-3 is substantially the same as the configuration of the positive electrode 21 of embodiment 4-1 shown in Figure 16C.

[0122] [Effects] In the positive electrode 21 of aspect 4-3, the undercoat layer 21C is provided to improve heat dissipation, while the masking layer 21D and the positive electrode active material layer 21B protect the undercoat layer 21C. Furthermore, because the undercoat layer 21C is also present below the masking layer 21D in the thickness direction, i.e., the T direction, it is possible to suppress peeling caused by the difference in hardness between the positive electrode active material layer 21B and the masking layer 21D when the positive electrode active material layer 21B is applied thickly. Furthermore, because the masking layer 21D is also in contact with the positive electrode current collector 21A, it is possible to effectively suppress peeling.

[0123] (4-4-1) [Configuration] Figure 17 is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 of embodiment 4-4-1 that can be used in batteries such as lithium-ion secondary batteries. As shown in Figure 17, in the positive electrode 21 of embodiment 4-4-1, undercoat layers 21C-a and 21C-b, positive electrode active material layers 21B-a and 21B-b, and masking layers 21D-a and 21D-b are formed on both surfaces (referred to as surface A and surface B for convenience) of a positive electrode current collector 21A. In the positive electrode 21 of embodiment 4-4-1, similar to the positive electrode 21 of embodiment 4-3 shown in Figure 16C, the undercoat layers 21C-a and 21C-b are covered with masking layers 21D-a and 21D-b and positive electrode active material layers 21B-a and 21B-b.

[0124] In the positive electrode 21 of aspect 4-4-1, in the W direction, the position of the tip T21D-a of the masking layer 21D-a is set back from the position of the tip T21A of the positive electrode current collector 21A, the position of the tip T21D-b of the masking layer 21D-b is set back from the position of the tip T21D-a, the position of the tip T21C-a of the undercoat layer 21C-a is set back from the position of the tip T21D-b, the position of the tip T21C-b of the undercoat layer 21C-b is set back from the position of the tip T21C-a, the position of the tip T21B-a of the positive electrode active material layer 21B-a is set back from the position of the tip T21C-b, and the position of the tip T21B-b of the positive electrode active material layer 21B-b is set back from the position of the tip T21B-a. In addition, in the direction W, the position of the rear end E21D-b of the masking layer 21D-b is set back from the position of the rear end E21D-a of the masking layer 21D-a. Furthermore, in the direction T, which corresponds to the thickness direction, the distance M-Ha between the surface of the masking layer 21D-a at the position of the tip T21C-a of the undercoat layer 21C-a and the surface A of the positive electrode current collector 21A is smaller than the distance M-Hb between the surface of the masking layer 21D-b at the position of the tip T21C-b of the undercoat layer 21C-b and the surface B of the positive electrode current collector 21A (M-Ha<M-Hb).

[0125] [Effect] In the positive electrode 21 of aspect 4-4-1, the position of the tip T21D-a of the masking layer 21D-a is closer to the position of the tip T21A of the positive electrode current collector 21A in the W direction than the position of the tip T21D-b of the masking layer 21D-b, and the distance M-Ha is shorter than the distance M-Hb, making it easier to bend the first end of the positive electrode current collector 21A. That is, the positive electrode current collector 21A is easier to bend with the position of the tip T21D-b as a fulcrum. As a result, bending stress is less likely to be transmitted to the undercoat layers 21C-a and 21D-b formed on both sides of the positive electrode current collector 21A, and occurrences such as peeling of the undercoat layers 21C-a and 21D-b can be suppressed.

[0126] In contrast, as in embodiment 4-4-2A shown in Figure 18A, the position of the tip T21D-a of the masking layer 21D-a is closer to the position of the tip T21A of the positive electrode current collector 21A than the position of the tip T21D-b of the masking layer 21D-b in the W direction, and if the thickness of the masking layer 21D-a is greater than the thickness of the masking layer 21D-b, it becomes difficult to fold the positive electrode current collector 21A at the position of the tip T21D-b. Similarly, as in embodiment 4-4-2B shown in Figure 18B, the position of the tip T21D-b of the masking layer 21D-b is closer to the position of the tip T21A of the positive electrode current collector 21A than the position of the tip T21D-a of the masking layer 21D-a in the W direction, and if the thickness of the masking layer 21D-b is greater than the thickness of the masking layer 21D-a, it becomes difficult to fold the positive electrode current collector 21A at the position of the tip T21D-a.

[0127] (4-4-3A) [Configuration] Figure 19A is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 of embodiment 4-4-3A that can be applied to a battery such as a lithium-ion secondary battery. In the positive electrode 21 of embodiment 4-4-3A, the position of the tip T21D-a of the masking layer 21D-a and the position of the tip T21D-b of the masking layer 21D-b are substantially the same in the W direction. Furthermore, the position of the tip T21C-a of the undercoat layer 21C-a is closer to the tip T21A of the positive electrode current collector 21A than the position of the tip T21C-b of the undercoat layer 21C-b. In this case, it is preferable that the thickness of the masking layer 21D-a is thinner than the thickness of the masking layer 21D-b.

[0128] [Effect] In the positive electrode 21 of aspect 4-4-3A, the position of the tip T21D-a of the masking layer 21D-a and the position of the tip T21D-b of the masking layer 21D-b are substantially the same in the W direction, and the distance M-Ha is shorter than the distance M-Hb, making it easier to bend the first end of the positive electrode current collector 21A. That is, the positive electrode current collector 21A is easier to bend around the positions of the tips T21D-a and T21D-b as fulcrums. As a result, bending stress is less likely to be transmitted to the undercoat layers 21C-a and 21D-b formed on both sides of the positive electrode current collector 21A, and peeling of the undercoat layers 21C-a and 21D-b can be suppressed.

[0129] (4-4-3B) [Configuration] Figure 19B is an enlarged cross-sectional view showing the configuration of a portion of the positive electrode 21 of embodiment 4-4-3B, which can be applied to a battery such as a lithium-ion secondary battery. In the positive electrode 21 of embodiment 4-4-3B, in the W direction, the position of the tip T21D-b of the masking layer 21D-b is closer to the tip T21A of the positive electrode current collector 21A than the position of the tip T21D-a of the masking layer 21D-a. Also, the position of the tip T21C-a of the undercoat layer 21C-a is closer to the tip T21A of the positive electrode current collector 21A than the position of the tip T21C-b of the undercoat layer 21C-b. In this case, it is preferable that the thickness of the masking layer 21D-b is thinner than the thickness of the masking layer 21D-a.

[0130] [Effect] In the positive electrode 21 of aspect 4-4-3B, the distance between the position of the tip T21D-b of the masking layer 21D-b and the position of the tip T21A of the positive electrode current collector 21A in the W direction is closer than the distance between the position of the tip T21D-a of the masking layer 21D-a and the position of the tip T21A of the positive electrode current collector 21A, and the distance M-Hb is shorter than the distance M-Ha. This makes it easier to bend the first end of the positive electrode current collector 21A. In other words, it is easier to bend the positive electrode current collector 21A with the position of the tip T21D-a as a fulcrum. This makes it harder for bending stress to be transmitted to the undercoat layers 21C-a and 21D-b formed on both sides of the positive electrode current collector 21A, thereby suppressing the occurrence of peeling of the undercoat layers 21C-a and 21D-b.

[0131] (4-5) [Configuration] FIG. 20 is an enlarged cross-sectional view showing a partial configuration of a positive electrode 21 of embodiment 4-5 that can be used in a battery such as a lithium-ion secondary battery. As shown in FIG. 20, in the positive electrode 21 of embodiment 4-5, the position of the tip T21C of the undercoat layer 21C is recessed inward in the W direction from both the position of the tip T21D of the masking layer 21D and the position of the tip T21B of the positive electrode active material layer 21B. Therefore, the undercoat layer 21C is covered by the masking layer 21D and the positive electrode active material layer 21B. Except for this, the configuration of the positive electrode 21 of embodiment 4-5 is substantially the same as the configuration of the positive electrode 21 of embodiment 4-1 shown in FIG. 4-1. Note that in embodiment 4-5, the position of the tip T21D of the masking layer 21D is closer to the tip T21A of the positive electrode current collector 21A in the W direction than the position of the tip T21B of the positive electrode active material layer 21B.

[0132] [Effects] In the positive electrode 21 of aspect 4-5, the undercoat layer 21C is also provided, thereby reducing electrical resistance and suppressing heat generation during high-load charge / discharge. Furthermore, the undercoat layer 21C improves heat dissipation and suppresses heat generation during high-load charge / discharge. Furthermore, in the positive electrode 21 of aspect 4-5, the tip T21C of the undercoat layer 21C is positioned further back than the tip T21B of the positive electrode active material layer 21B. This reduces the reduction in end surface density due to sagging of the positive electrode active material layer 21B and the variation in volume density of the positive electrode active material layer 21B due to the masking layer 21D, thereby enabling a more uniform battery reaction to be expected.

[0133] (4-6) [Configuration] Figure 21A is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 according to embodiment 4-6A that can be used in a battery such as a lithium-ion secondary battery. As shown in Figure 21A, in the positive electrode 21 according to embodiment 4-6A, the positions at which the positive electrode active material layers 21B-a and 21B-b are formed are specified to match the positions at which the undercoat layers 21C-a and 21C-b are formed. Specifically, in the W direction, the tip T21B-a of the positive electrode active material layer 21B-a is set at a position that is further back from the tip T21A of the positive electrode current collector 21A than the position of the tip T21C-a of the undercoat layer 21C-a formed on the surface (referred to as surface A for convenience) of the positive electrode current collector 21A. In the W direction, a tip T21B-b of the positive electrode active material layer 21B-b is set at a position that is more recessed from the tip T21A of the positive electrode current collector 21A than the position of a tip T21C-b of the undercoat layer 21C-b formed on the back surface (referred to as surface B for convenience) of the positive electrode current collector 21A. Here, as shown in FIG. 21A , if the position of the tip T21C-a is closer to the tip T21A of the positive electrode current collector 21A than the position of the tip T21C-b in the W direction, the position of the tip T21B-a will be closer to the tip T21A of the positive electrode current collector 21A than the position of the tip T21B-b.

[0134] [Effects] The positive electrode 21 of aspect 4-6A also includes an undercoat layer 21C, which reduces electrical resistance and suppresses heat generation during high-load charge / discharge. Furthermore, the undercoat layer 21C improves heat dissipation and suppresses heat generation during high-load charge / discharge. Furthermore, the stability of the positions (linearity and area density) of the tip T21B-a of the positive electrode active material layer 21B-a and the tip T21B-b of the positive electrode active material layer 21B-b in the W direction relative to the L direction can be ensured. Furthermore, the releasability of the undercoat layer 21C can be ensured.

[0135] In contrast, for example, as shown in FIG. 21B, when the position of the tip T21B-a of the positive electrode active material layer 21B-a is closer to the tip T21A of the positive electrode current collector 21A than the position of the tip T21C-a of the undercoat layer 21C-a, or when the position of the tip T21B-b of the positive electrode active material layer 21B-b is closer to the tip T21A of the positive electrode current collector 21A than both the position of the tip T21C-a of the undercoat layer 21C-a and the position of the tip T21C-b of the undercoat layer 21C-b, it is difficult to expect the above-mentioned effect.

[0136] (4-7) [Configuration] Fig. 22A is a schematic plan view showing the configuration of a portion of a positive electrode 21 of Aspect 4-7A that can be applied to a battery such as a lithium-ion secondary battery. As shown in Fig. 22A, in the positive electrode 21 of Aspect 4-7A, a tip T21B in the W direction of the positive electrode active material layer 21B extends in a substantially straight line along the L direction, which is the longitudinal direction of the positive electrode 21. Specifically, the position of the tip T21B in the W direction may be within a range of ±50 µm with respect to a reference position.

[0137] [Effect] When bending an exposed portion of the positive electrode current collector 21A that is not covered by the positive electrode active material layer 21B, stress is less likely to be concentrated on the positive electrode current collector 21A near the tip T21B when the tip T21B in the W direction of the positive electrode active material layer 21B has unevenness in the L direction, as in the positive electrode 21 of Aspect 4-7B as a reference example shown in Fig. 22B , and therefore damage to the positive electrode current collector 21A can be avoided.

[0138] (4-8) [Configuration] Fig. 23A is a cross-sectional schematic diagram showing the configuration of a portion of the electrode winding body 20 of Aspect 4-8A that can be applied to a battery such as a lithium-ion secondary battery. As shown in Fig. 23A, in the electrode winding body 20 of Aspect 4-8A, a portion of the negative electrode current collector 22A that is exposed on the end surface facing the negative electrode current collector 25 is covered with an undercoat layer 22C. That is, on the end surface of the electrode winding body 20 facing the negative electrode current collector 25, the edge of the undercoat layer 22C extends further toward the negative electrode current collector 25 than the edge of the negative electrode active material layer 22B.

[0139] 23B is a cross-sectional schematic diagram showing the configuration of a portion of the electrode winding 20 of Aspect 4-8B that can be applied to a battery such as a lithium-ion secondary battery. As shown in FIG. 23B , in the electrode winding 20 of Aspect 4-8B, as in the electrode winding 20 of Aspect 4-8A, a portion of the negative electrode current collector 22A exposed on the end surface facing the negative electrode current collector 25 is covered with an undercoat layer 22C. That is, on the end surface of the electrode winding 20 facing the negative electrode current collector 25, the edge of the undercoat layer 22C extends further toward the negative electrode current collector 25 than the edge of the negative electrode active material layer 22B. In particular, in Aspect 4-8B, the undercoat layer 22C extends to a position closer to the negative electrode current collector 25 than the position where the negative electrode current collector 22A is bent.

[0140] 23C is a cross-sectional schematic diagram illustrating the configuration of a portion of the electrode winding body 20 of Example 4-8C as a reference example. As shown in FIG. 23C, in the electrode winding body 20 of Example 4-8C, the edge of the negative electrode active material layer 22B and the edge of the undercoat layer 22C are aligned on the end face of the electrode winding body 20 facing the negative electrode current collector plate 25.

[0141] [Effect] In the electrode wound body 20 of Aspect 4-8C, when the negative electrode current collector 22A is welded to the negative electrode current collector plate 25, the expansion of the electrode wound body 20 causes the negative electrode current collector 22A to be stretched. This may result in damage such as cracks occurring in the negative electrode current collector 22A. In the electrode wound bodies 20 of Aspects 4-8A and 4-8B, the negative electrode current collector 22A is reinforced by the undercoat layer 22C, so damage to the negative electrode current collector 22A can be avoided. In particular, the electrode wound body 20 of Aspect 4-8B is preferable because it further reinforces the negative electrode current collector 22A.

[0142] 24 is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 according to embodiment 4-9 that can be used in batteries such as lithium-ion secondary batteries. As shown in FIG. 24, in the positive electrode 21 according to embodiment 4-9, the thicknesses of the undercoat layers 21C-a and 21C-b increase in the W direction with increasing distance from the positions of the tips T21B-a and T21B-b of the positive electrode active material layer 21B.

[0143] [Effects] In the positive electrode 21 of aspect 4-9, the undercoat layers 21C-a and 21C-b are provided, thereby reducing electrical resistance and suppressing heat generation during high-load charge and discharge. Furthermore, the undercoat layers 21C-a and 21C-b are provided, improving heat dissipation and suppressing heat generation during high-load charge and discharge. Furthermore, in the positive electrode 21 of aspect 4-9, the thickness of the undercoat layers 21C-a and 21C-b increases with increasing distance from the positions of the tips T21B-a and T21B-b of the positive electrode active material layer 21B, while the thickness of the positive electrode active material layers 21B-a and 21B-b decreases with increasing distance from the positions of the tips T21B-a and T21B-b. This reduces the resistance at positions far from the exposed portion of the positive electrode current collector 21A welded to the positive electrode current collector 24, allowing for a more uniform electrode reaction in the W direction.

[0144] (4-10) [Configuration] Figure 25 is an enlarged cross-sectional view showing the configuration of a portion of the positive electrode 21 of six embodiments 4-10(A) to (F) that can be applied to batteries such as lithium-ion secondary batteries. Each of the positive electrodes 21 of embodiments 4-10(A) to (F) has a structure in which an undercoat layer 21C and a positive electrode active material layer 21B are sequentially laminated on both sides of a positive electrode current collector 21A. In the positive electrodes 21 of embodiments 4-10(A) to (F), the positive electrode current collector 21A includes a first edge T21A and a second edge E21A in the W direction, and has an exposed region near the first edge T21A that is not covered by either the undercoat layer 21C or the positive electrode active material layer 21B.

[0145] As shown in (A) of Figure 25, in the positive electrode 21 of embodiment 4-10(A), the thickness of the undercoat layer 21C in the W direction becomes thinner as it moves away from both the first edge T21A of the positive electrode current collector 21A and the second edge E22A of the positive electrode current collector 21A, and is thinnest near the middle between the first edge T21A and the second edge E22A.

[0146] As shown in (B) of Figure 25, in the positive electrode 21 of embodiment 4-10(B), the thickness of the undercoat layer 21C in the W direction increases with increasing distance from both the first edge T21A of the positive electrode current collector 21A and the second edge E22A of the positive electrode current collector 21A, and is thickest near the middle between the first edge T21A and the second edge E22A.

[0147] As shown in (C) of Figure 25, in the positive electrode 21 of embodiment 4-10(C), in the W direction, the undercoat layer 21C has relatively thick portions near both the first edge T21A of the positive electrode current collector 21A and the second edge E22A of the positive electrode current collector 21A, and has a relatively thin portion near the middle between the first edge T21A and the second edge E22A.

[0148] As shown in (D) of Figure 25, in the positive electrode 21 of embodiment 4-10(D), in the W direction, the undercoat layer 21C has relatively thin portions near both the first edge T21A of the positive electrode current collector 21A and the second edge E22A of the positive electrode current collector 21A, and has a relatively thick portion near the middle between the first edge T21A and the second edge E22A.

[0149] 25(E), in the positive electrode 21 of embodiment 4-10(E), the thickness of the undercoat layer 21C is formed to be approximately constant in the W direction, and another undercoat layer 21C2 is selectively formed on the undercoat layer 21C in regions near both the first edge T21A of the positive electrode current collector 21A and the second edge E22A of the positive electrode current collector 21A. The composition of the undercoat layer 21C and the composition of the undercoat layer 21C2 are different from each other. For example, the binder ratio of the undercoat layer 21C is 1% relative to the entire undercoat layer 21C, while the binder ratio of the undercoat layer 21C2 is 0.5% relative to the entire undercoat layer 21C2. The undercoat layer 21C in contact with the positive electrode current collector 21A preferably has a ratio that ensures adhesion to the positive electrode current collector 21A, and the undercoat layer 21C2 has a lower binder ratio than the undercoat layer 21C in order to reduce resistance in the thickness direction. Because the undercoat layer 21C is in contact with the positive electrode current collector 21A, a powdered conductive material such as acetylene black is preferred in order to reduce resistance in the surface direction, and the undercoat layer 21C2 preferably uses a fibrous conductive material such as carbon nanotubes in order to form a conductive path in the thickness direction.

[0150] As shown in (F) of Figure 25, in the positive electrode 21 of embodiment 4-10(F), the thickness of the undercoat layer 21C is formed to be approximately constant in the W direction, and another undercoat layer 21C2 is selectively formed on the undercoat layer 21C in the middle region in the W direction.

[0151] In a battery including an electrode winding 20 to which the positive electrode 21 of any of the above-described embodiments 4-10(A) to (F) is applied, current collecting portions are disposed at both ends in the W direction. In the electrode winding 20, the current collection efficiency is high near the current collecting portion, and decreases with increasing distance from the current collecting portion. Therefore, compared to a case in which the thickness of the undercoat layer 21C in the middle region far from the current collecting portion is greater than the thickness of the undercoat layer 21C in the end regions close to the current collecting portion, as in the positive electrode 21 of embodiment 4-10(B) and embodiment 4-10(D), a case in which the thickness of the undercoat layer 21C in the end regions close to the current collecting portion is greater than the thickness of the undercoat layer 21C in the middle region far from the current collecting portion, as in the positive electrode 21 of embodiment 4-10(A) and embodiment 4-10(C), the variation in current collection efficiency in the W direction can be reduced. As a result, capacity loss during charge / discharge cycles can be suppressed, and heat generation during high-load use can be uniformed, thereby suppressing battery degradation. The undercoat layer 21C having a gradient thickness in the positive electrode 21 of embodiment 4-10(A) can be formed, for example, by gradually changing the amount of coating in the W direction. Furthermore, the undercoat layer 21C in which the thickness of both end regions is relatively greater than the thickness of the middle region in the W direction, as in the positive electrode 21 of embodiment 4-10(C), can be formed, for example, by coating an undercoat layer of a constant thickness over the entire surface and then selectively coating an additional undercoat layer only in the both end regions.

[0152] (4-11) [Configuration] Figure 26 is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 according to embodiment 4-11, which can be used in a battery such as a lithium-ion secondary battery. As shown in Figure 26, in the positive electrode 21 according to embodiment 4-11, in the W direction, the position of the tip T21D of the masking layer 21D is between the position of the tip T21A of the positive electrode current collector 21A and the position of the tip T21C of the undercoat layer 21C. Furthermore, in the W direction, the position of the tip T21C of the undercoat layer 21C is between the position of the tip T21D of the masking layer 21D and the position of the tip T21B of the positive electrode active material layer 21B. Here, the thickness M-Ha of the portion of the masking layer 21D that directly covers the positive electrode current collector 21A is thinner than the total thickness M-Hb of the undercoat layer 21C and the portion of the masking layer 21D that covers the undercoat layer 21C. The thickness M-Hb is smaller than the total thickness M-Hc of the portion of the masking layer 21D that covers both the undercoat layer 21C and the positive electrode active material layer 21B, the undercoat layer 21C, and the positive electrode active material layer 21B.

[0153] [Effects] In the positive electrode 21 of aspect 4-11, the undercoat layer 21C is provided, thereby reducing electrical resistance and suppressing heat generation during high-load charge / discharge. Furthermore, the undercoat layer 21C improves heat dissipation and suppresses heat generation during high-load charge / discharge. Furthermore, the undercoat layer 21C can be protected by the masking layer 21D. Furthermore, the vicinity of the tip T21B of the positive electrode active material layer 21B is covered by the masking layer 21D, thereby preventing the positive electrode active material layer 21B from falling off. Furthermore, the masking layer 21D directly covers a portion of the exposed portion of the positive electrode current collector 21A, thereby preventing misalignment of the wound electrode body 20.

[0154] (4-12) In the positive electrode 21 of the above embodiments 4-1 to 4-11, the surface density (or thickness) of the undercoat layer 21C-a formed on the surface A of the positive electrode current collector 21A may be different from the surface density (or thickness) of the undercoat layer 21C-b formed on the surface B of the positive electrode current collector 21A. For example, in the portion bent with a high curvature located at the center of the winding of the electrode winding body 20, the thickness of the positive electrode active material layer 21B provided on the surface of the positive electrode current collector 21A near the center of the winding is increased, so the surface density (or thickness) of the undercoat layer 21C is increased. This reduces resistance, adjusts the potential distribution, and homogenizes the heat generation distribution. As a result, a longer life can be expected.

[0155] (4-13) [Configuration] FIG. 27 is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 according to embodiment 4-13, which can be used in a battery such as a lithium-ion secondary battery. As shown in FIG. 27, in the positive electrode 21 according to embodiment 4-13, an undercoat layer 21C is provided on only one side of the positive electrode current collector 21A (e.g., the surface toward the center of the winding of the electrode winding body 20). The side of the positive electrode current collector 21A on which the undercoat layer 21C is not provided is welded to the positive electrode current collector 24. In the W direction, the position of the tip T21C of the undercoat layer 21C may, for example, substantially coincide with the position of the tip T21A of the positive electrode current collector 21A. Furthermore, in the W direction, the position of the tip T21D of the masking layer 21D is recessed from the position of the tip T21A of the positive electrode current collector 21A and the position of the tip T21C of the undercoat layer 21C. In addition, in the W direction, the position of the tip T21D of the masking layer 21D is, for example, between the position of the tip T21C of the undercoat layer 21C and the position of the tip T21B of the positive electrode active material layer 21B. The undercoat layer 21C is made of, for example, small particle carbon.

[0156] [Effect] If any damage is present on the surface of the positive electrode current collector 21A that is closer to the winding center of the electrode winding body 20, cracks are likely to occur in the positive electrode current collector 21A during the production of the electrode winding body 20 or during charge / discharge cycles after completion. Therefore, by applying an undercoat layer 21C made of small particles of carbon or the like, stress concentration due to large particles of the active material contained in the positive electrode active material layer 21B during pressing is reduced, making cracks and breakage of the positive electrode current collector 21A less likely to occur. Note that in the positive electrode 21 of aspect 4-13, the undercoat layer 21C may be applied over the entire surface of one side of the positive electrode current collector 21A (it does not have to be a patterned undercoat layer 21C).

[0157] (4-14) [Configuration] Fig. 28A is an enlarged cross-sectional view showing the configuration of a portion of a positive electrode 21 according to embodiment 4-14 that can be applied to a battery such as a lithium-ion secondary battery. Specifically, Fig. 28A is an image obtained by observing a 3 mm x 3 mm cross section, which is prepared by cutting the positive electrode 21 according to embodiment 4-14 with a razor blade or an ion milling device, and which includes the interface between a positive electrode current collector 21A and an undercoat layer 21C and a positive electrode active material layer 21B, using an electron microscope at a magnification of 2000 times. However, the volume density of the positive electrode 21 shown in Fig. 28A is 3.0 g / cm ３ 28A is observed at three locations with a viewing angle of 60 μm×40 μm, it is preferable that the ratio (FL / CL) of the length CL of the portion where the positive electrode active material layer 21B is in direct contact with the positive electrode current collector 21A to the length FL of the positive electrode current collector 21A is 20% or less.

[0158] [Effect] To reduce the interface resistance between the positive electrode current collector 21A and the positive electrode active material layer 21B, an undercoat layer 21C formed by applying a carbon material can be used. FIG. 28B is a characteristic diagram showing the relationship between the presence or absence of the carbon coating layer 21C and the interface resistance between the positive electrode current collector 21A and the positive electrode active material layer 21B. As shown in FIG. 28B, the presence of the undercoat layer 21C reduces the interface resistance and the composite resistance. Therefore, it is preferable to have the undercoat layer 21C interposed between the positive electrode current collector 21A and the positive electrode active material layer 21B rather than having them directly contact each other. However, depending on the compression conditions during pressing when fabricating the positive electrode 21, the positive electrode active material layer 21B may penetrate the carbon coating layer 21C and come into contact with the positive electrode current collector 21A. In this case, the interface resistance and the composite resistance increase. Therefore, FL / CL, which means the proportion of the positive electrode active material layer 21B that penetrates the undercoat layer 21C and comes into contact with the positive electrode current collector 21A, is preferably 20% or less. If it is 20% or less, the effect of reducing the interface resistance and the composite resistance can be sufficiently expected.

[0159] (4-15) [Configuration] FIG. 29A is an enlarged cross-sectional view showing the configuration of a portion of an electrode wound body 20 according to embodiment 4-15-1, which can be used in batteries such as lithium-ion secondary batteries. As shown in FIG. 29A , in the electrode wound body 20 according to embodiment 4-15-1, the positive electrode 21 includes a positive electrode current collector 21A, undercoat layers 21C provided on both sides of the positive electrode current collector 21A, and a positive electrode active material layer 21B provided on the undercoat layer 21C, but does not include a masking layer. A portion of the positive electrode current collector 21A is not covered by either the undercoat layer 21C or the positive electrode active material layer 21B and is exposed. That is, in the W direction, the tip T21C of the undercoat layer 21C is positioned further back than the tip T21A of the positive electrode current collector 21A. Furthermore, in the W direction, the tip T21B of the positive electrode active material layer 21B is positioned further back than the tip T21C. In addition, a negative electrode 22 is provided on the opposite side of the positive electrode 21 in the T direction, with the separator 23 sandwiched therebetween. In the negative electrode 22, a negative electrode active material layer 22B is provided on both sides of a negative electrode current collector 22A. In the W direction, the position of a tip T22B of the negative electrode active material layer 22B is between the positions of the tips T21C and T21B.

[0160] 29B is an enlarged cross-sectional view showing the configuration of a portion of the electrode wound body 20 of Aspect 4-15-2 that can be applied to batteries such as lithium-ion secondary batteries. In the electrode wound body 20 of Aspect 4-15-2 shown in FIG. 29B, a ceramic coating layer CCS is provided on the surface of the separator 23 that faces the positive electrode 21. Except for this point, the configuration of the electrode wound body 20 of Aspect 4-15-2 is substantially the same as the configuration of the electrode wound body 20 of Aspect 4-15-1.

[0161] 29C is an enlarged cross-sectional view showing the configuration of a portion of the electrode wound body 20 of Aspect 4-15-3 that can be used in batteries such as lithium-ion secondary batteries. In the electrode wound body 20 of Aspect 4-15-3 shown in FIG. 29C, the undercoat layer 21C is provided only near the tip T21B of the positive electrode active material layer 21B. Except for this, the configuration of the electrode wound body 20 of Aspect 4-15-3 is substantially the same as the configuration of the electrode wound body 20 of Aspect 4-15-2.

[0162] [Effects] In the positive electrodes 21 of Aspects 4-15-1 to 4-15-3, the undercoat layer 21C is provided, thereby reducing electrical resistance and suppressing heat generation during high-load charge / discharge. Furthermore, the undercoat layer 21C improves heat dissipation and suppresses heat generation during high-load charge / discharge. Furthermore, since no masking layer is provided to cover the undercoat layer 21C or the positive electrode active material layer 21B, this is more suitable for improving energy density than when a masking layer is provided, and the manufacturing process is simplified.

[0163] (4-16) [Configuration] Fig. 30A is an enlarged cross-sectional view showing the configuration of a positive electrode 21 of Aspect 4-16 that can be applied to a battery such as a lithium-ion secondary battery. Fig. 30B is a schematic plan view showing the configuration of the positive electrode 21 of Aspect 4-16. In the positive electrode 21 of Aspect 4-16, the laser absorptance of the undercoat 21C is higher than that of the positive electrode current collector 21A. In a region of the positive electrode current collector 21A that is covered with the undercoat layer 21C but not covered with the positive electrode active material layer 21B, multiple locations indicated by arrows are cut by laser irradiation.

[0164] [Effect] By coating the positive electrode current collector 21A with the undercoat 21C having a high laser absorptivity before processing, it is possible to suppress deterioration and deformation of the positive electrode current collector 21A due to heat generated during laser cutting, and as a result, the laser cutting can be performed efficiently.

[0165] (5-1) [Configuration] Fig. 31 is a schematic diagram showing the cathode active material particles 21BP and polyvinylidene fluoride (PVdF) contained in the cathode active material layer 21B of embodiment 5-1, which can be used in a battery such as a lithium ion secondary battery. The PVdF is made porous by utilizing phase separation during drying. For example, it can be obtained by adding NMP (N-methyl-2-pyrrolidone) and TEG (triethylene glycol) as a poor solvent to PVdF.

[0166] [Effects] According to the positive electrode active material layer 21B of Aspect 5-1, flexibility is improved by making the PVdF porous. This allows the positive electrode active material layer 21B to be made thicker. That is, even if the thickness of the positive electrode active material layer 21B is increased, the positive electrode active material layer 21B has high flexibility, so that the winding operation when producing the electrode wound body 20 can be carried out smoothly. Furthermore, by making the PVdF porous, a path for lithium ions in the positive electrode active material layer 21B is secured. This allows the ionic resistance of the electrode wound body 20 to be reduced, and further higher output can be expected.

[0167] (5-2) [Configuration] Fig. 32 is a schematic diagram showing a cathode 21 of embodiment 5-2 that can be used in a battery such as a lithium-ion secondary battery, and cathode active material particles 21BP and polyvinylidene fluoride (PVdF) contained in a cathode active material layer 21B. As shown in Fig. 32, the cathode 21 of embodiment 5-2 includes a cathode current collector 21A and cathode active material layers 21B provided on both sides of the cathode current collector 21A. The cathode active material layer 21B includes, in order from the cathode current collector 21A side, a first region 21B1 and a second region 21B2.

[0168] The first region 21B1 includes a plurality of positive electrode active material particles 21BP connected via gelled PVdF, and the second region 21B2 includes a plurality of positive electrode active material particles 21BP connected via porous PVdF.

[0169] [Effects] According to the cathode active material layer 21B of Aspect 5-2, the second region 21B2 contains porous PVdF, resulting in high flexibility. This allows for a thicker cathode active material layer 21B. That is, even when the cathode active material layer 21B is thick, the layer 21B remains highly flexible, facilitating the winding process when fabricating the electrode wound body 20. Furthermore, by making the PVdF porous, a path for lithium ions in the second region 21B2 is ensured. This reduces the ionic resistance of the electrode wound body 20, potentially enabling even higher output. Meanwhile, because the first region 21B1 contains non-porous gel-like PVdF, a strong bond between the first region 21B1 and the cathode current collector 21A can be obtained, preventing the cathode active material layer 21B from peeling or falling off from the cathode current collector 21A.

[0170] (5-3) [Configuration] Fig. 33 is a cross-sectional schematic diagram showing a positive electrode 21 of Aspect 5-3 that can be applied to a battery such as a lithium-ion secondary battery. As shown in Fig. 33, the positive electrode 21 of Aspect 5-3 includes a positive electrode current collector 21A and positive electrode active material layers 21B provided on both sides of the positive electrode current collector 21A. The positive electrode active material layer 21B includes, in order from the positive electrode current collector 21A side, a first region 21B1 and a second region 21B2.

[0171] Here, the ratio of the binder such as PVdF contained in the second region 21B2 is higher than the ratio of the binder such as PVdF contained in the first region 21B1.

[0172] [Effects] According to the positive electrode active material layer 21B of Aspect 5-3, the binder content relative to the positive electrode active material is increased in the second region 21B2 located on the surface of the positive electrode 21. The surface of the positive electrode 21 is a location where stress is likely to concentrate, for example, when the positive electrode 21 is wound to produce the wound electrode body 20. By increasing the binder ratio near the surface of the positive electrode 21, it is possible to effectively prevent cracks from occurring in the positive electrode active material layer 21B. Furthermore, it is possible to reduce the binder content compared to when a large amount of binder is uniformly dispersed throughout the positive electrode active material layer 21B.

[0173] (5-4) [Configuration] Fig. 34 is a cross-sectional schematic diagram showing a positive electrode 21 of Aspect 5-4 that can be applied to a battery such as a lithium-ion secondary battery. As shown in Fig. 34, the positive electrode 21 of Aspect 5-4 includes a positive electrode current collector 21A and a positive electrode active material layer 21B provided on the surface thereof. The positive electrode active material layer 21B includes, in order from the positive electrode current collector 21A side, a first region 21B1 and a second region 21B2.

[0174] Here, the ratio of the binder such as PVdF contained in the first region 21B1 is higher than the ratio of the binder such as PVdF contained in the second region 21B2.

[0175] [Effects] In the positive electrode active material layer 21B of aspect 5-4, the binder ratio in the first region 21B1 adjacent to the positive electrode current collector 21A is higher than the binder ratio in the second region 21B2. This increases the adhesion between the positive electrode current collector 21A and the positive electrode active material layer 21B, making it difficult for the positive electrode active material layer 21B to peel from the positive electrode current collector 21A. In other words, the peel resistance of the positive electrode active material layer 21B can be increased. As a result, improved load characteristics can be expected. In addition, the binder content can be reduced compared to when a large amount of binder is uniformly dispersed throughout the positive electrode active material layer 21B.

[0176] (5-5) [Configuration] FIG. 35 is a cross-sectional schematic diagram illustrating an electrode winding 20 according to aspect 5-5 that can be used in batteries such as lithium-ion secondary batteries. As shown in FIG. 35, the electrode winding 20 according to aspect 5-5 is formed by winding a laminated structure in which a positive electrode 21 and a negative electrode 22 are stacked with a separator interposed therebetween. The negative electrode 22 is located at the innermost periphery of the electrode winding 20. The positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B provided on both sides thereof. The positive electrode active material layer 21B has portions in which relatively thick film portions 21B-A and relatively thin film portions 21B-B are alternately arranged in the winding direction. The thin film portions 21B-B are located in portions other than the outermost periphery of the electrode winding 20 and extend, for example, in the width direction perpendicular to the winding direction.

[0177] [Effect] According to the positive electrode active material layer 21B of Aspect 5-5, the thin film portion 21B-B is provided, which can mitigate the expansion of the electrode winding body 20 that accompanies the expansion of the negative electrode 22 during charging. As a result, it is possible to prevent a portion of the positive electrode 21 from buckling toward the through-hole 26 at the center of the electrode winding body 20.

[0178] (5-6) [Configuration] Fig. 36 is a cross-sectional schematic diagram showing an electrode winding 20 of Aspect 5-6 that can be applied to a battery such as a lithium-ion secondary battery. As shown in Fig. 36, the electrode winding 20 of Aspect 5-6 is formed by winding a laminated structure in which a positive electrode 21 and a negative electrode 22 are stacked with a separator interposed therebetween. The negative electrode 22 is present at the innermost periphery of the electrode winding 20. Here, the positive electrode active material layer 21B is not provided at the innermost periphery of the positive electrode 21 that faces the negative electrode active material layer 22B at the innermost periphery of the negative electrode 22. In other words, the negative electrode active material layer 22B at the innermost periphery of the negative electrode 22 faces the positive electrode current collector 21A of the positive electrode 21 located on the outer side.

[0179] [Effect] According to the positive electrode active material layer 21B of Aspect 5-6, the positive electrode active material layer 21B is not provided in the innermost peripheral portion of the positive electrode 21 that faces the negative electrode active material layer 22B in the innermost peripheral portion of the negative electrode 22, thereby making it possible to suppress expansion of the innermost peripheral portion of the negative electrode 22 during charging. As a result, it is possible to prevent a portion of the positive electrode 21 from buckling toward the through-hole 26 at the center of the electrode winding body 20.

[0180] (5-7) [Configuration] Fig. 37A is a cross-sectional schematic diagram illustrating a positive electrode 21 according to Aspect 5-7-1 that can be used in a battery such as a lithium-ion secondary battery. As shown in Fig. 37A, the positive electrode 21 according to Aspect 5-7-1 includes a positive electrode current collector 21A, a positive electrode active material layer 21B provided on the surface of the positive electrode current collector 21A, and an insulating layer 21Z. In the L direction, the positive electrode current collector 21A and the positive electrode active material layer 21B each extend from the winding center edge 21E1 of the positive electrode 21 to the winding outer peripheral edge 21E2. That is, in the L direction, the position of the tip T21B1 of the positive electrode active material layer 21B coincides with the position of the tip T21A1 of the positive electrode current collector 21A, and the position of the tip T21B2 of the positive electrode active material layer 21B coincides with the position of the tip T21A2 of the positive electrode current collector 21A. The insulating layer 21Z covers the tip T21B1 of the positive electrode active material layer 21B and its vicinity, and the tip T21B2 of the positive electrode active material layer 21B and its vicinity. As in the positive electrode 21 of embodiment 5-7-2 shown in FIG. 37B , the insulating layer 21Z1 may be provided so as to extend beyond the winding center side edge 21E1 in the L direction, or may be provided so as to extend beyond the winding outer peripheral side edge 21E2 in the L direction. Furthermore, a portion of the insulating layer 21Z may permeate the positive electrode active material layer 21B.

[0181] [Effects] According to the positive electrode 21 of Aspects 5-7-1 and 5-7-2, the insulating layer 21Z is provided, so that the tips T21B1, T21B2 of the positive electrode active material layer 21B and their vicinity can be protected. The provision of the insulating layer 21Z suppresses shedding of the positive electrode active material at the tips T21B1, T21B2 of the positive electrode active material layer 21B and their vicinity, and suppresses dust generation from the positive electrode 21. As a result, a reduction in the open circuit voltage (OCV) defect rate and suppression of short circuit occurrence during storage can be expected.

[0182] Furthermore, the insulating layer 21Z acts as a buffer material, alleviating stress on the separator 23 caused by expansion and contraction of the electrode winding body 20 during charge and discharge cycles. Furthermore, the insulating layer 21Z acts as a buffer material, reducing friction between the positive electrode 21 and the separator 23 caused by expansion and contraction of the electrode winding body 20 during charge and discharge cycles, preventing the positive electrode active material from falling off from the positive electrode active material layer 21B, and avoiding unintended exposure of the positive electrode current collector 21A. As a result, the insulating layer 21Z acts as a buffer material and an insulating material, effectively suppressing the occurrence of short circuits during charge and discharge cycles.

[0183] (5-8) [Configuration] FIG. 38A is a cross-sectional schematic diagram illustrating an electrode winding 20 according to aspect 5-8 that can be used in batteries such as lithium-ion secondary batteries. The electrode winding 20 according to aspect 5-8 is formed by winding a laminated structure in which a positive electrode 21 and a negative electrode 22 are stacked with a separator interposed therebetween. As shown in FIG. 38A , the innermost circumferential portion of the positive electrode 21 of the electrode winding 20 according to aspect 5-8 is wound with at least one turn of the positive electrode current collector 21A that is not covered by the positive electrode active material layer 21B. FIG. 38B is a plan view of the positive electrode 21 of the electrode winding 20 according to aspect 5-8 in which the positive electrode 21 is unfolded. As shown in FIG. 38B , the positive electrode 21 has an exposed portion near the upper edge in the W direction, where part of the positive electrode current collector 21A is not covered by the positive electrode active material layer 21B and is exposed. The positive electrode 21 is provided with an insulating layer 21D straddling the boundary K-W between the exposed portion of the positive electrode current collector 21A in the W direction and the portion where the positive electrode active material layer 21B covers the exposed portion of the positive electrode. The positive electrode 21 also has an exposed portion where a portion of the positive electrode current collector 21A is not covered by the positive electrode active material layer 21B near the end edge 21E1 on the winding center side in the L direction. The positive electrode 21 is provided with an insulating layer 21F straddling the boundary K-L between the exposed portion of the positive electrode current collector 21A in the L direction and the portion where the positive electrode active material layer 21B covers the exposed portion of the positive electrode current collector 21A. Here, in the W direction, the position of the tip T21F of the insulating layer 21F is between the position of the tip T21A of the positive electrode current collector 21A and the position of the tip T21B of the positive electrode active material layer 21B. Furthermore, in the W direction, the insulating layer 21D is provided at a position recessed inward from the position of the tip T21A of the positive electrode current collector 21A. That is, both the insulating layer 21F and the insulating layer 21D are provided at a position away from the position of the tip T21A of the positive electrode current collector 21A in the W direction. Note that the vicinity of the outer winding edge 21E2 of the positive electrode 21 in the L direction may also have the same structure as the vicinity of the central winding edge 21E1 of the positive electrode 21 in the L direction. Note that the insulating layer 21F and the insulating layer 21D may be, for example, tapes made of an insulating material attached to the positive electrode current collector 21A and the positive electrode active material layer 21B, or may be coating layers formed by applying an insulating material so as to cover the boundary K-W and its vicinity, and the boundary K-L and its vicinity, respectively.

[0184] [Effects] According to the positive electrode 21 of aspect 5-8, only the positive electrode current collector 21A of the positive electrode 21 is wound one or more times at the innermost circumferential portion of the electrode winding 20. This increases the inner diameter of the electrode winding 20 at the portion where the positive electrode active material layer 21B is provided. This reduces the stress applied to the positive electrode active material layer 21B due to expansion of the negative electrode 22 during charge / discharge cycles, for example. As a result, damage such as cracking of the positive electrode active material layer 21B is avoided. Furthermore, buckling at the innermost circumferential portion of the positive electrode 21 can be suppressed, thereby preventing internal short circuits. Furthermore, the insulating layer 21F and the insulating layer 21D are both located away from the tip T21A of the positive electrode current collector 21A in the W direction, thereby ensuring good conductive bonding between the positive electrode current collector 21A and the positive electrode current collector.

[0185] (5-9) [Configuration] Figure 39 is a cross-sectional schematic diagram showing an electrode winding body 20 of embodiment 5-9 that can be applied to a battery such as a lithium-ion secondary battery. In the electrode winding body 20 of embodiment 5-9, an area of ​​the outer surface of the positive electrode current collector 21A at the innermost circumferential portion thereof, extending up to a position 3.6 mm from the winding start end, is covered with an insulating layer 21D. Note that the insulating layers 21F and 21D may be, for example, tapes made of an insulating material attached to the positive electrode current collector 21A and the positive electrode active material layer 21B, or may be coating layers formed by applying an insulating material so as to cover the boundary K-W and its vicinity, and the boundary K-L and its vicinity, respectively.

[0186] [Effect] According to the positive electrode 21 of aspect 5-9, for example, when a laminate structure including the positive electrode 21 and the negative electrode 22 is wound to produce the wound electrode body 20, even if a crack or the like occurs in the positive electrode active material layer 21B, the insulating layer 21D can prevent the positive electrode active material layer 21B from falling off. As a result, a positive electrode active material layer 21B with a high in-plane density can be realized.

[0187] 40A is a schematic diagram showing anode active material particles 22BP and porous CMC (carboxymethyl cellulose) contained in anode active material layer 22B of embodiment 6-1 that can be applied to a battery such as a lithium ion secondary battery. The porous CMC is a binder present in the gaps between a plurality of anode active material particles 22BP. The porous CMC is foamed and made porous by adding, for example, NMP (N-methyl-2-pyrrolidone) as a poor solvent.

[0188] [Effect] According to the negative electrode active material layer 22B of Aspect 6-1, the CMC is made porous to form paths for lithium ions. Therefore, lithium ions can easily permeate the CMC. Therefore, even if the negative electrode active material layer 22B is made thick, the ionic resistance of the electrode wound body 20 can be reduced, and further higher output can be expected.

[0189] 40B is a micrograph showing an enlarged view of anode active material particles 22BP and porous CMC (carboxymethyl cellulose) included in anode active material layer 22B of embodiment 6-2, which can be used in a battery such as a lithium-ion secondary battery. The porous CMC is a binder that covers at least a portion of the surface of anode active material particles 22BP. The porous CMC is foamed and made porous by adding, for example, NMP (N-methyl-2-pyrrolidone) as a poor solvent.

[0190] [Effect] According to the anode active material layer 22B of aspect 6-2, the surfaces of the anode active material particles 22BP are covered with porous CMC, which makes it easier for lithium ions to permeate the CMC and reach the anode active material particles 22BP compared to when the surfaces of the anode active material particles 22BP are covered with solid, non-porous CMC. Therefore, even when the anode active material layer 22B is made thick, the ionic resistance of the electrode wound body 20 can be reduced, and further higher output can be expected.

[0191] (6-3) [Configuration] Figure 40C is a cross-sectional schematic diagram illustrating an anode 22 of Aspect 6-3 that can be used in a battery such as a lithium-ion secondary battery. As shown in Figure 40C, the anode 22 of Aspect 6-3 includes an anode current collector 22A, an anode active material layer 22B provided on the surface thereof, and a masking layer 22D. In the W direction, the position of the tip T22B of the anode active material layer 22B is set back more inward than the position of the tip T22A of the anode current collector 22A. Therefore, a portion of the anode current collector 22A is exposed and not covered by the anode active material layer 22B. The masking layer 22D covers the exposed portion of the anode current collector 22A and the vicinity of the tip T22B of the anode active material layer 22B.

[0192] [Effect] According to the negative electrode 22 of Aspect 6-3, the masking layer 22D is provided, so that the vicinity of the tip T22B of the negative electrode active material layer 22B can be protected. By providing the masking layer 22D, it is possible to suppress the shedding of the negative electrode active material near the tip T22B of the negative electrode active material layer 22B and to suppress the generation of dust from the negative electrode 22. As a result, it is expected that the open circuit voltage (OCV) defect rate will be reduced and the occurrence of short circuits during storage will be suppressed.

[0193] Furthermore, the masking layer 22D functions as a buffer material, alleviating stress on the separator 23 caused by expansion and contraction of the electrode wound body 20 during charge and discharge cycles. Furthermore, the masking layer 22D functions as a buffer material, reducing friction between the negative electrode 22 and the separator 23 caused by expansion and contraction of the electrode wound body 20 during charge and discharge cycles, preventing the negative electrode active material from falling off from the negative electrode active material layer 22B, and avoiding unintended exposure of the negative electrode current collector 22A. As a result, the masking layer 22D functions as a buffer material and an insulating material, and can effectively suppress the occurrence of short circuits during charge and discharge cycles.

[0194] (7-1) [Configuration] Fig. 41 is a cross-sectional schematic diagram showing an electrode wound body 20 of embodiment 7-1 that can be applied to a battery such as a lithium-ion secondary battery. As shown in Fig. 41, the electrode wound body 20 of embodiment 7-1 is formed by winding a laminate in which a positive electrode 21, a separator 23, a negative electrode 22, and a separator 23 are stacked in this order. In the electrode wound body 20 of embodiment 7-1, the negative electrode 22 is present at the outermost periphery, rather than the separator 23. More specifically, the outermost periphery of the electrode wound body 20 of embodiment 7-1 is the outer surface of the wound negative electrode current collector 22A, such as copper foil.

[0195] [Effects] According to the electrode winding body 20 of Aspect 7-1, the negative electrode current collector 22A is exposed on the outermost peripheral surface thereof, improving heat dissipation and enabling the heat generated by the battery reaction to be efficiently discharged to the outside. In addition, the length of the separator 23 of the electrode winding body 20 can be reduced, thereby improving the capacity of a battery including the electrode winding body 20.

[0196] (7-2) [Configuration] The electrode wound body of Aspect 7-2, which can be applied to batteries such as lithium ion secondary batteries, is a wound laminate in which a positive electrode, a separator, a negative electrode, and a separator are stacked in this order. In the electrode wound body of Aspect 7-2, a negative electrode is present at the outermost periphery, rather than a separator. More specifically, the outermost periphery of the electrode wound body of Aspect 7-2 is the outer surface of a negative electrode current collector such as copper foil. In the electrode wound body of Aspect 7-2, a negative electrode is also present at the innermost periphery, rather than a separator.

[0197] [Effects] According to the electrode wound body of Aspect 7-2, the negative electrode current collector is exposed on the outermost and innermost peripheral surfaces thereof, improving heat dissipation and enabling the heat generated by the battery reaction to be efficiently discharged to the outside. In addition, the length of the separator of the electrode wound body can be reduced, thereby improving the capacity of a battery including the electrode wound body.

[0198] (7-3) [Configuration] The wound electrode body of aspect 7-3, which can be applied to batteries such as lithium ion secondary batteries, is formed by winding a laminate in which a positive electrode, a separator, a negative electrode, and a separator are stacked in this order. However, in the wound electrode body of aspect 7-3, of the positive electrode, the separator, and the negative electrode, only the separator is present in the central portion of the winding. In the central portion of the winding, only the separator of the positive electrode, the separator, and the negative electrode is wound multiple times.

[0199] [Effects] According to the electrode wound body of Aspect 7-3, since only the separator of the positive electrode, separator, and negative electrode is wound multiple times in the central winding portion, even if stress is applied to the positive electrode active material layer due to expansion of the negative electrode during charging, for example, the positive electrode active material layer can withstand the stress, thereby preventing cracks and buckling from occurring in the positive electrode active material layer.

[0200] (7-4) [Configuration] Fig. 42 is a cross-sectional schematic diagram showing an electrode wound body 20 of Aspect 7-4 that can be applied to a battery such as a lithium ion secondary battery. As shown in Fig. 42, the electrode wound body 20 of Aspect 7-4 is formed by winding a laminate in which a positive electrode, a separator, a negative electrode, and a separator are stacked in this order. In the electrode wound body 20 of Aspect 7-4, a sheet-like insulating member Z is provided on at least one of a portion of the surface of the positive electrode and a portion of the surface of the negative electrode. The insulating member Z has a predetermined length in the winding direction. The insulating member Z may be provided at multiple locations in the winding direction.

[0201] [Effect] According to the electrode wound body 20 of aspect 7-4, the insulating member Z is provided, and therefore a step corresponding to the thickness of the insulating member Z is generated on at least one of the surfaces of the positive electrode and the negative electrode. As a result, even if the negative electrode expands during charging, multiple locations where stress concentrates are generated inside the electrode wound body 20, and it is possible to eliminate locations where large stress concentrates locally. As a result, it is possible to avoid cracking or detachment of the positive electrode active material layer, or cracks or breakage in the separator, thereby improving safety.

[0202] (7-6) [Configuration] FIG. 43A is an enlarged cross-sectional view of the upper end portion in the height direction Z of the electrode winding 20 of Aspect 7-6, which can be used in batteries such as lithium-ion secondary batteries. FIG. 43B is an enlarged cross-sectional view of the lower end portion in the height direction Z of the electrode winding 20 of Aspect 7-6. As shown in FIG. 43A , the upper end portion of the electrode winding 20 has a compressed positive electrode current collector portion 21CS. The compressed positive electrode current collector portion 21CS is a portion of the positive electrode current collector (e.g., aluminum foil) constituting the electrode winding 20, in which multiple upper edges adjacent in the radial direction of the electrode winding (the lateral direction of the paper in FIG. 43A ) are compressed so as to overlap each other in the height direction Z without sandwiching a separator. The upper surface of the compressed positive electrode current collector portion 21CS is joined to, for example, a positive electrode current collector plate. On the other hand, as shown in FIG. 43B , the lower end of the electrode winding 20 has a compressed negative electrode current collector portion 22CS. The compressed negative electrode current collector portion 22CS is a portion of the negative electrode current collector (e.g., copper foil) constituting the electrode winding 20, in which multiple lower edges adjacent in the electrode winding radial direction (the lateral direction of the paper in FIG. 43B ) are compressed and crushed so that they overlap each other in the height direction Z without sandwiching a separator. The lower surface of the compressed negative electrode current collector portion 22CS is joined to, for example, a negative electrode current collector plate. Here, the maximum value of the thickness (dimension in the height direction Z) H21CS of the compressed positive electrode current collector portion 21CS is greater than the maximum value of the thickness (dimension in the height direction Z) H22CS of the compressed negative electrode current collector portion 22CS.

[0203] [Effect] According to the electrode winding body 20 of aspect 7-6, the maximum value of the thickness H21CS of the compressed positive current collector portion 21CS is greater than the maximum value of the thickness H22CS of the compressed negative current collector portion 22CS. This allows for a balanced reduction in the connection resistance between the compressed positive current collector portion 21CS and the positive current collector plate, and in the connection resistance between the compressed negative current collector portion 22CS and the negative current collector.

[0204] (8-1) The negative electrode current collector of embodiment 8-1 is made of high-purity copper foil. Specifically, it is made of copper foil with a purity of 99.99% or higher. Such copper foil can achieve a volume resistivity of 0.1677 μΩ·m or lower and a thermal conductivity of 400 W / (m·k) or higher. Using such copper foil as the negative electrode current collector suppresses heat generation during high input / output, suppresses temperature rise in the secondary battery, and achieves good cycle characteristics. Furthermore, for example, thermal conductivity between the negative electrode current collector and the negative electrode current collector plate is improved, allowing heat generated in the electrode winding to be efficiently dissipated to the outside via the negative electrode current collector plate and the outer can. As a result, good cycle characteristics are achieved. Furthermore, the high-purity copper foil has excellent ductility, which can also suppress the occurrence of cracks in the negative electrode current collector due to expansion and contraction during charge and discharge.

[0205] (8-2) [Configuration] FIG. 44 is a cross-sectional schematic diagram illustrating the vicinity of the upper end surface 41 of the electrode winding 20 in the secondary battery of aspect 8-2. The upper edge of the positive current collector that forms the upper end surface 41 of the electrode winding 20 is welded to the positive current collector 24. Here, a gap G1, which is the amount of deviation in the radial direction of the electrode winding 20 between the outer edge of the electrode winding 20 and the outer edge of the positive current collector 24, is less than 1 mm. Furthermore, a gap G2, which is the amount of deviation in the radial direction of the electrode winding 20 between the inner edge of the through-hole 26 in the electrode winding 20 and the inner edge of the opening 35 in the positive current collector 24, is less than 0.5 mm. In other words, most of the area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive current collector 24. Similarly, in the secondary battery of embodiment 8-2, it is preferable that most of the area of ​​the lower end surface 42 of the electrode winding body 20 is joined to the negative electrode current collector plate 25 .

[0206] [Effects] The secondary battery of Aspect 8-2 is expected to have improved high-load discharge characteristics, and to have an effect of suppressing the occurrence of short circuits during charge-discharge cycles and during high-temperature storage.

[0207] (8-3-1) [Configuration] FIG. 45A is a cross-sectional schematic diagram showing the vicinity of the upper end surface 41 of the electrode winding body 20 in the secondary battery of Aspect 8-3-1. In the secondary battery of Aspect 8-3-1, the electrode winding body 20 has a first region 20-1, a second region 20-2, and a third region 20-3, arranged in this order in the height direction Z of the secondary battery. The first region 20-1 is a region where the positive electrode and the negative electrode are stacked and wound with a separator interposed therebetween. The second region 20-2 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are arranged apart from each other in the radial direction R of the secondary battery without overlapping each other. The third region 20-3 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are compressed and crushed so that they overlap each other, resulting in the presence of compressed portions. The top surface of the third region 20-3 is the upper end surface 41 of the electrode winding 20, and the upper end surface 41 is joined to the positive current collector 24 by welding or the like. In the secondary battery of Aspect 8-3-1, the inner diameter D35 of the opening 35 of the positive current collector 24 is smaller than the inner diameter D26 of the through hole 26 of the electrode winding 20. Therefore, a portion of the positive current collector 24 extends so as to protrude into the through hole 26. Note that in the secondary battery of Aspect 8-3-1, the outer diameter of the electrode winding 20 and the outer diameter of the positive current collector 24 are substantially the same.

[0208] [Effects] In the secondary battery of Aspect 8-3-1, the inner diameter D35 of the opening 35 in the positive current collector 24 is smaller than the inner diameter D26 of the through-hole 26 in the electrode winding 20, and almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive current collector 24. This is expected to improve high-load discharge characteristics, suppress the occurrence of short circuits during charge / discharge cycles, and suppress the occurrence of short circuits during high-temperature storage. Note that in the secondary battery of Aspect 8-3-1, it is preferable to make the inner diameter of the opening 36 in the negative current collector 25 smaller than the inner diameter D26 of the through-hole 26 in the electrode winding 20, so that almost the entire area of ​​the lower end surface 42 of the electrode winding 20 is joined to the negative current collector 25.

[0209] (8-3-2) [Configuration] FIG. 45B is a cross-sectional schematic diagram showing the vicinity of the upper end surface 41 of the electrode winding body 20 in the secondary battery of Aspect 8-3-2. In the secondary battery of Aspect 8-3-2, the electrode winding body 20 has a first region 20-1, a second region 20-2, and a third region 20-3, arranged in this order in the height direction Z of the secondary battery. The first region 20-1 is a region where the positive electrode and the negative electrode are stacked and wound with a separator interposed therebetween. The second region 20-2 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are arranged apart from each other in the radial direction R of the secondary battery without overlapping each other. The third region 20-3 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are compressed and crushed so that they overlap each other, resulting in the presence of compressed portions. The upper surface of the third region 20-3 forms the upper end surface 41 of the electrode winding 20, and the upper end surface 41 is joined to the positive current collector 24 by welding or the like. In the secondary battery of aspect 8-3-2, the third region 20-3 has a recess 20U1 on its inner peripheral edge. The recess 20U1 is formed on the inner peripheral edge of a compressed portion of the positive current collector in the third region 20-3, i.e., a portion where multiple portions of the positive current collector not covered by the positive active material layer overlap each other. The recess 20U1 is a portion where the inner peripheral edge of the compressed portion of the positive current collector in the third region 20-3 is bent toward the outer periphery. Note that the inner diameter D26 of the through hole 26 in the electrode winding 20, excluding the portion where the recess 20U1 is provided, and the inner diameter D35 of the opening 35 in the positive current collector 24 are substantially the same. However, the inner diameter D35 may be smaller than the inner diameter D26. In the secondary battery of Example 8-3-2, the outer diameter of the electrode winding body 20 and the outer diameter of the positive electrode current collector plate 24 are substantially the same.

[0210] [Effects] In the secondary battery of Aspect 8-3-2, almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive electrode current collector 24. Furthermore, because the third region 20-3 has the recess 20U1, buckling at the innermost circumferential portion of the electrode winding 20 is suppressed, for example, when expansion of the negative electrode occurs during charging. This can be expected to improve high-load discharge characteristics, suppress short circuit occurrence during charge / discharge cycles, and suppress short circuit occurrence during high-temperature storage. In the secondary battery of Aspect 8-3-2, it is also preferable that the negative electrode current collector has a portion where the inner circumferential edge of the compressed portion is bent toward the outer circumferential side.

[0211] (8-3-3) [Configuration] FIG. 45C is a cross-sectional schematic diagram showing the vicinity of the upper end surface 41 of the electrode winding body 20 in the secondary battery of Aspect 8-3-3. In the secondary battery of Aspect 8-3-3, the electrode winding body 20 has a first region 20-1, a second region 20-2, and a third region 20-3, arranged in this order in the height direction Z of the secondary battery. The first region 20-1 is a region where the positive electrode and the negative electrode are stacked and wound with a separator interposed therebetween. The second region 20-2 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are arranged apart from each other in the radial direction R of the secondary battery without overlapping each other. The third region 20-3 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are compressed and crushed so that they overlap each other, resulting in the presence of compressed portions. The upper surface of the third region 20-3 forms the upper end surface 41 of the electrode winding 20, and the upper end surface 41 is joined to the positive current collector 24 by welding or the like. In the secondary battery of Aspect 8-3-3, the inner diameter D35 of the opening 35 of the positive current collector 24 is smaller than the inner diameter D26 of the through hole 26 of the electrode winding 20. Therefore, a portion of the positive current collector 24 extends so as to protrude into the through hole 26. Furthermore, a bent portion 24T1 bent toward the inside of the through hole 26 is provided at the peripheral edge of the opening 35 of the positive current collector 24. The bent portion 24T1 covers at least a portion of the inner peripheral edge of the third region 20-3. Note that in the secondary battery of Aspect 8-3-3, the outer diameter of the electrode winding 20 and the outer diameter of the positive current collector 24 are substantially the same.

[0212] [Effects] In the secondary battery of Aspect 8-3-3, almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive electrode current collector 24. Furthermore, the inner peripheral edge of the third region 20-3 is covered by the folded portion 24T1 of the positive electrode current collector 24. Therefore, for example, when the negative electrode expands during charging, buckling at the innermost peripheral portion of the electrode winding 20 is suppressed. This can be expected to improve high-load discharge characteristics, suppress short circuit occurrence during charge / discharge cycles, and suppress short circuit occurrence during high-temperature storage. Note that in the secondary battery of Aspect 8-3-3, the negative electrode current collector 25 may also have a folded portion around the periphery of the opening 36, so that the folded portion of the negative electrode current collector 25 covers at least a portion of the inner peripheral edge near the lower end surface 42 of the electrode winding 20.

[0213] (8-3-4) [Configuration] FIG. 45D is a cross-sectional schematic diagram showing the vicinity of the upper end surface 41 of the electrode winding 20 in the secondary battery of Aspect 8-3-4. In the secondary battery of Aspect 8-3-4, the electrode winding 20 has a first region 20-1, a second region 20-2, and a third region 20-3, arranged in this order in the height direction Z of the secondary battery. The first region 20-1 is a region where the positive electrode and the negative electrode are stacked and wound with a separator interposed therebetween. The second region 20-2 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are arranged apart from each other in the radial direction R of the secondary battery without overlapping each other. The third region 20-3 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are compressed and crushed so that they overlap each other, resulting in the presence of compressed portions. The upper surface of the third region 20-3 forms the upper end surface 41 of the electrode winding 20, and the upper end surface 41 is joined to the positive current collector 24 by welding or the like. In the secondary battery of Aspect 8-3-4, the inner diameter D35 of the opening 35 of the positive current collector 24 is smaller than the inner diameter D26 of the through-hole 26 of the electrode winding 20. Therefore, a portion of the positive current collector 24 extends so as to protrude into the through-hole 26. Furthermore, in the secondary battery of Aspect 8-3-4, the third region 20-3 has a recess 20U1 on its inner peripheral edge. The recess 20U1 is a position where the inner peripheral edge of the compressed portion of the positive current collector in the third region 20-3 is bent toward the outer periphery. Furthermore, a bent portion 24T1 is provided on the peripheral edge of the opening 35 of the positive current collector 24. The bent portion 24T1 covers at least a part of the recess 20U1 of the third region 20-3. In the secondary battery of Example 8-3-4, the outer diameter of the electrode winding body 20 and the outer diameter of the positive current collector plate 24 are substantially the same.

[0214] [Effects] In the secondary battery of Aspect 8-3-4, almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive electrode current collector 24. Furthermore, at least a portion of the recess 20U1 provided on the inner peripheral edge of the third region 20-3 is covered by the folded portion 24T1 of the positive electrode current collector 24. Therefore, for example, when the negative electrode expands during charging, buckling at the innermost peripheral portion of the electrode winding 20 is suppressed. This can be expected to improve high-load discharge characteristics, suppress short circuit occurrence during charge / discharge cycles, and suppress short circuit occurrence during high-temperature storage. Note that in the secondary battery of Aspect 8-3-4, the negative electrode current collector 25 may also have a folded portion provided on the periphery of the opening 36 and a recess provided on the inner peripheral edge near the lower end surface 42 of the electrode winding 20, so that the folded portion of the negative electrode current collector 25 covers the recess of the electrode winding 20.

[0215] (8-4-1) [Configuration] FIG. 46A is a cross-sectional schematic diagram showing the vicinity of the upper end surface 41 of the electrode winding body 20 in the secondary battery of Aspect 8-4-1. In the secondary battery of Aspect 8-4-1, the electrode winding body 20 has a first region 20-1, a second region 20-2, and a third region 20-3, arranged in this order in the height direction Z of the secondary battery. The first region 20-1 is a region where the positive electrode and the negative electrode are stacked and wound with a separator interposed therebetween. The second region 20-2 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are arranged apart from each other in the radial direction R of the secondary battery without overlapping each other. The third region 20-3 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are compressed and crushed so that they overlap each other, resulting in the presence of compressed portions. The upper surface of the third region 20-3 forms the upper end surface 41 of the electrode winding 20, and the upper end surface 41 is joined to the positive current collector 24 by welding or the like. In the secondary battery of Aspect 8-4-1, the third region 20-3 has a recess 20U2 on its outer peripheral edge. The recess 20U2 is a portion where the outer peripheral edge of the compressed portion of the positive current collector present in the third region 20-3 is bent toward the inner peripheral side. Note that the inner diameter D26 of the through hole 26 in the electrode winding 20 and the inner diameter D35 of the opening 35 in the positive current collector 24 are substantially the same. However, the inner diameter D35 may be smaller than the inner diameter D26.

[0216] [Effects] In the secondary battery of Aspect 8-4-1, almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive electrode current collector 24. Furthermore, because the third region 20-3 has the recess 20U2, even if the negative electrode expands during charging, for example, misalignment between the outermost peripheral portion of the electrode winding 20 and the outermost peripheral portion of the positive electrode current collector 24 is unlikely to occur. This improves current collection efficiency. Furthermore, improved high-load discharge characteristics and suppression of short circuit occurrence during charge / discharge cycles and high-temperature storage can be expected. In the secondary battery of Aspect 8-4-1, the negative electrode current collector may also have a portion where the outer peripheral edge of its compressed portion is bent toward the outer periphery.

[0217] (8-4-2) [Configuration] FIG. 46B is a cross-sectional schematic diagram showing the vicinity of the upper end surface 41 of the electrode winding 20 in the secondary battery of Aspect 8-4-2. In the secondary battery of Aspect 8-4-2, the electrode winding 20 has a first region 20-1, a second region 20-2, and a third region 20-3, arranged in this order in the height direction Z of the secondary battery. The first region 20-1 is a region where the positive electrode and the negative electrode are stacked and wound with a separator interposed therebetween. The second region 20-2 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are arranged apart from each other in the radial direction R of the secondary battery without overlapping each other. The third region 20-3 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are compressed and crushed so that they overlap each other, resulting in the presence of compressed portions. The upper surface of the third region 20-3 forms the upper end surface 41 of the electrode winding 20, and the upper end surface 41 is joined to the positive current collector 24 by welding or the like. In the secondary battery of Aspect 8-4-2, the outer diameter of the positive current collector 24 is larger than the outer diameter of the electrode winding 20. Therefore, a portion of the positive current collector 24 extends so as to protrude outward beyond the third region 20-3 of the electrode winding 20. Furthermore, the outer peripheral edge of the positive current collector 24 is provided with a bent portion 24T2 that is bent toward the negative current collector 25. The bent portion 24T2 covers at least a portion of the outer peripheral edge of the third region 20-3. Note that in the secondary battery of Aspect 8-4-2, the inner diameter D26 of the through hole 26 in the electrode winding 20 and the inner diameter D35 of the opening 35 in the positive current collector 24 are substantially the same.

[0218] [Effects] In the secondary battery of Aspect 8-4-2, almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive current collector 24. Furthermore, the outer peripheral edge of the third region 20-3 is covered by the folded portion 24T of the positive current collector 24. Therefore, even if the negative electrode expands during charging, for example, the position of the outermost portion of the electrode winding 20 is unlikely to shift from the position of the outermost portion of the positive current collector 24. This improves current collection efficiency. Furthermore, improved high-load discharge characteristics, suppression of short circuit occurrence during charge / discharge cycles, and suppression of short circuit occurrence during high-temperature storage can be expected. In the secondary battery of Aspect 8-4-2, it is preferable that the negative current collector 25 also has a folded portion at its outer peripheral edge, so that the folded portion of the negative current collector 25 covers at least a portion of the outer peripheral edge near the lower end surface 42 of the electrode winding 20.

[0219] (8-4-3) [Configuration] FIG. 46C is a cross-sectional schematic diagram showing the vicinity of the upper end surface 41 of the electrode winding 20 in the secondary battery of Aspect 8-4-3. In the secondary battery of Aspect 8-4-3, the electrode winding 20 has a first region 20-1, a second region 20-2, and a third region 20-3, arranged in this order in the height direction Z of the secondary battery. The first region 20-1 is a region where the positive electrode and the negative electrode are stacked and wound with a separator interposed therebetween. The second region 20-2 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are arranged apart from each other in the radial direction R of the secondary battery without overlapping each other. The third region 20-3 is a region where, in the wound positive electrode, multiple upper end portions of the positive electrode current collector that are not covered with the positive electrode active material layer are compressed and crushed so that they overlap each other, resulting in the presence of compressed portions. The upper surface of the third region 20-3 forms the upper end surface 41 of the electrode winding 20, and the upper end surface 41 is joined to the positive current collector 24 by welding or the like. In the secondary battery of Aspect 8-4-2, the outer diameter of the positive current collector 24 is larger than the outer diameter of the electrode winding 20. Therefore, a portion of the positive current collector 24 extends outward beyond the third region 20-3 of the electrode winding 20. Furthermore, in the secondary battery of Aspect 8-4-3, the third region 20-3 has a recess 20U2 on its outer peripheral edge. The recess 20U2 is a position where the outer peripheral edge of the compressed portion of the positive current collector in the third region 20-3 is bent toward the inner peripheral side. Furthermore, a bent portion 24T2 is provided on the outer peripheral edge of the positive current collector 24. The bent portion 24T2 covers at least a portion of the recess 20U2 of the third region 20-3. In the secondary battery of Example 8-4-3, the inner diameter D26 of the through-hole 26 of the electrode winding body 20 and the inner diameter D35 of the opening 35 of the positive electrode current collector plate 24 are substantially equal to each other.

[0220] [Effects] In the secondary battery of aspect 8-4-3, almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive electrode current collector 24. Furthermore, at least a portion of the recess 20U2 provided on the outer peripheral edge of the third region 20-3 is covered by the folded portion 24T2 of the positive electrode current collector 24. Therefore, even if the negative electrode expands during charging, for example, the position of the outermost portion of the electrode winding 20 is unlikely to shift from the position of the outermost portion of the positive electrode current collector 24. This improves current collection efficiency. In addition, improved high-load discharge characteristics, suppression of short circuits during charge / discharge cycles, and suppression of short circuits during high-temperature storage can be expected. In the secondary battery of aspect 8-4-3, it is preferable that a bent portion is also provided on the outer peripheral edge of the negative electrode current collector 25, and that a recess is provided on the outer peripheral edge near the lower end face 42 of the electrode winding body 20, so that the bent portion of the negative electrode current collector 25 covers the recess of the electrode winding body 20.

[0221] (8-5-1) [Configuration] FIG. 47A is a cross-sectional schematic diagram illustrating the vicinity of the upper end surface 41 of the electrode winding 20 in the secondary battery of Aspect 8-5-1. In the secondary battery of Aspect 8-5-1, the outer diameter of the positive current collector 24 is larger than the outer diameter of the electrode winding 20. Therefore, a portion of the positive current collector 24 extends so as to protrude outward from the third region 20-3 of the electrode winding 20. Furthermore, a bent portion 24T2 is provided on the outer peripheral edge of the positive current collector 24. The bent portion 24T2 covers at least a portion of the outer peripheral edge of the third region 20-3. Furthermore, in the secondary battery of Aspect 8-5-1, the inner diameter D35 of the opening 35 of the positive current collector 24 is smaller than the inner diameter D26 of the through-hole 26 of the electrode winding 20. Therefore, a portion of the positive current collector 24 extends so as to protrude into the through-hole 26. Furthermore, a bent portion 24T1 is provided on the periphery of the opening 35 of the positive current collector plate 24, bending toward the inside of the through-hole 26. The bent portion 24T1 covers at least a part of the inner circumferential edge of the third region 20-3.

[0222] [Effects] In the secondary battery of aspect 8-5-1, almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive electrode current collector 24. Furthermore, the outer peripheral edge of the third region 20-3 is covered by the folded portion 24T2 of the positive electrode current collector 24. Therefore, even if the negative electrode expands during charging, for example, misalignment between the outermost peripheral portion of the electrode winding 20 and the outermost peripheral portion of the positive electrode current collector 24 is unlikely to occur. This improves current collection efficiency. Furthermore, improved high-load discharge characteristics, suppression of short circuit occurrence during charge / discharge cycles, and suppression of short circuit occurrence during high-temperature storage can be expected. Furthermore, the inner peripheral edge of the third region 20-3 is covered by the folded portion 24T1 of the positive electrode current collector 24. Therefore, even if the negative electrode expands during charging, for example, buckling at the innermost peripheral portion of the electrode winding 20 is suppressed. Therefore, it is possible to expect improvements in high-load discharge characteristics, an effect of suppressing the occurrence of short circuits during charge / discharge cycles, and an effect of suppressing the occurrence of short circuits during high-temperature storage. In the secondary battery of Aspect 8-5-1, it is also preferable to provide a folded portion on the outer peripheral edge of the negative current collector 25 so that the folded portion of the negative current collector 25 covers at least a part of the outer peripheral edge near the lower end surface 42 of the electrode winding 20. Furthermore, it is preferable to provide a folded portion on the periphery of the opening 36 so that the folded portion of the negative current collector 25 covers at least a part of the inner peripheral edge near the lower end surface 42 of the electrode winding 20.

[0223] (8-5-2) [Configuration] FIG. 47B is a cross-sectional schematic diagram illustrating the vicinity of the upper end surface 41 of the electrode winding 20 in the secondary battery of Example 8-5-2. In the secondary battery of Example 8-5-2, the outer diameter of the positive electrode current collector 24 is larger than the outer diameter of the electrode winding 20. Therefore, a portion of the positive electrode current collector 24 extends outward beyond the third region 20-3 of the electrode winding 20. Furthermore, in the secondary battery of Example 8-5-2, the third region 20-3 has a recess 20U2 on its outer peripheral edge. The recess 20U2 is a position where the outer peripheral edge of the compressed portion of the positive electrode current collector present in the third region 20-3 is bent toward the inner peripheral side. Furthermore, a bent portion 24T2 is provided on the outer peripheral edge of the positive electrode current collector 24. The bent portion 24T2 covers at least a portion of the recess 20U2 of the third region 20-3. Furthermore, in the secondary battery of Aspect 8-5-2, the inner diameter D35 of the opening 35 of the positive current collector 24 is smaller than the inner diameter D26 of the through-hole 26 of the electrode winding body 20. Therefore, a portion of the positive current collector 24 extends into the through-hole 26. Furthermore, in the secondary battery of Aspect 8-5-2, the third region 20-3 has a recess 20U1 at its inner peripheral edge. The recess 20U1 is a portion where the inner peripheral edge of the compressed portion of the positive current collector in the third region 20-3 is bent toward the outer periphery. Furthermore, a bent portion 24T1 is provided at the peripheral edge of the opening 35 of the positive current collector 24. The bent portion 24T1 covers at least a portion of the recess 20U1 of the third region 20-3.

[0224] [Effects] In the secondary battery of Aspect 8-5-2, almost the entire area of ​​the upper end surface 41 of the electrode winding 20 is joined to the positive electrode current collector 24. Furthermore, at least a portion of the recess 20U2 provided on the outer peripheral edge of the third region 20-3 is covered by the folded portion 24T2 of the positive electrode current collector 24. Therefore, even if the negative electrode expands during charging, for example, the position of the outermost portion of the electrode winding 20 is unlikely to shift from the position of the outermost portion of the positive electrode current collector 24. This improves current collection efficiency. Furthermore, improved high-load discharge characteristics, suppression of short circuit occurrence during charge / discharge cycles, and suppression of short circuit occurrence during high-temperature storage can be expected. Furthermore, in the secondary battery of Aspect 8-5-2, at least a portion of the recess 20U1 provided on the inner peripheral edge of the third region 20-3 is covered by the folded portion 24T1 of the positive electrode current collector 24. Therefore, for example, when the negative electrode expands during charging, buckling at the innermost circumferential portion of the electrode winding 20 is suppressed. Therefore, improved high-load discharge characteristics, suppression of short circuits during charge / discharge cycles, and suppression of short circuits during high-temperature storage can be expected. In the secondary battery of Aspect 8-5-2, the negative electrode current collector 25 may also be provided with a bent portion on the outer circumferential edge and a recess on the outer circumferential edge near the lower end surface 42 of the electrode winding 20, so that the bent portion of the negative electrode current collector 25 covers the recess in the electrode winding 20. Furthermore, in the secondary battery of Aspect 8-5-2, the negative electrode current collector 25 may also be provided with a bent portion on the periphery of the opening 36 and a recess on the inner circumferential edge near the lower end surface 42 of the electrode winding 20, so that the bent portion of the negative electrode current collector 25 covers the recess in the electrode winding 20.

[0225] (8-6) [Configuration] FIG. 48 is a schematic plan view illustrating the electrode winding 20 and the positive electrode current collector 24 of the secondary battery of Aspect 8-6. As shown in FIG. 48, in the secondary battery of Aspect 8-6, the electrode winding 20 and the sectorial portion 31 of the positive electrode current collector 24 are joined by welding or the like at multiple joining points WZ1 to WZ7. The joining points WZ2 to WZ7 extend radially along the radial direction of the secondary battery from an opening 35 at the center of the sectorial portion 31. The joining point WZ1 is located in the sectorial portion 31 near the boundary with the band-shaped portion 32. The band-shaped portion 32 is the portion that is joined to an external terminal. The length of the joining point WZ1 may be equal to or greater than the width of the band-shaped portion 32, for example.

[0226] [Effect] In the secondary battery of Aspect 8-6, the electrode winding body 20 and the positive current collector plate 24 are joined at the joining point WZ1 in addition to the joining points WZ2 to WZ7. This reduces the electrical resistance between the electrode winding body 20 and the positive current collector plate 24 compared to, for example, a case in which the electrode winding body 20 and the positive current collector plate 24 are joined only at the joining points WZ2 to WZ7. This is because the length of the conduction path between the joining point WZ1 and the strip portion 32 is shorter than the length of the conduction path between each of the joining points WZ2 to WZ7 and the strip portion 32. This reduces the internal resistance of the secondary battery of Aspect 8-6, thereby reducing the amount of heat generated. Furthermore, even if stress is applied to the boundary between the sectorial portion 31 and the strip-shaped portion 32 when expansion and contraction of the electrode winding body 20 occurs due to charging and discharging, because the sectorial portion 31 and the electrode winding body 20 are joined at the joint WZ1, a portion of the sectorial portion 31 is unlikely to peel off from the electrode winding body 20. Therefore, according to the secondary battery of aspect 8-6, the joint area between the sectorial portion 31 and the electrode winding body 20 is maintained, and therefore, operational reliability is excellent.

[0227] (9-1) [Configuration] In the secondary battery of embodiment 9-1, the electrode wound body 20 contains DMC (dimethyl carbonate) as the main solvent and LiPF 6 as the solute. ６ The non-aqueous electrolyte solution contains LiPF ６The content of DMC in the nonaqueous electrolyte is 12% by weight or less of the total weight of the nonaqueous electrolyte. The content of DMC in the nonaqueous electrolyte is 50% or more in terms of the molar ratio of carbonate contained in the nonaqueous electrolyte.

[0228] [Effects] According to the secondary battery of aspect 9-1, the low-viscosity solvent containing DMC as the main solvent contains LiPF 5 which has a viscosity increasing effect. ６ Since the electrode wound body 20 is impregnated with a non-aqueous electrolyte containing a predetermined amount of the above, it is possible to prevent the phenomenon of a small amount of non-aqueous electrolyte being isolated inside the secondary battery, and therefore it is possible to prevent dissolution of the metal forming the battery can.

[0229] (9-2) [Configuration] In the secondary battery of embodiment 9-2, the electrode wound body 20 contains DMC (dimethyl carbonate) as a main solvent, a cyclic carbonate as a sub-solvent, and LiPF 6 as a solute. ６ The nonaqueous electrolyte is impregnated with a nonaqueous electrolyte containing EC (ethylene carbonate), PC (propylene carbonate), and FEC (fluoroethylene carbonate). The cyclic carbonates in the nonaqueous electrolyte are EC (ethylene carbonate), PC (propylene carbonate), and FEC (fluoroethylene carbonate). The total content of EC, PC, and FEC in the nonaqueous electrolyte is 20% by weight or more of the total nonaqueous electrolyte, and the content of FEC is 10% by weight or more of the total nonaqueous electrolyte. The content of DMC in the nonaqueous electrolyte is 50% or more in terms of the molar ratio of carbonates contained in the nonaqueous electrolyte.

[0230] [Effects] According to the secondary battery of Aspect 9-2, the low-viscosity nonaqueous electrolyte solution having the above composition is impregnated into the electrode wound body 20, which prevents a small amount of nonaqueous electrolyte from being isolated inside the secondary battery, thereby preventing dissolution of the metal forming the battery can.

[0231] (9-3) [Configuration] In the secondary battery of Aspect 9-3, a swelling tape that swells when impregnated with an electrolyte solution is wound around the electrode wound body 20. For example, in the process of manufacturing the secondary battery of Aspect 9-3, the electrode wound body 20 wrapped with the swelling tape is inserted into the exterior can 11, and then the electrolyte solution is injected into the exterior can 11 to swell the swelling tape. As a result, the electrode wound body 20 and the exterior can 11 are in close contact with each other via the swelling tape, and the air layer between the electrode wound body 20 and the exterior can 11 is reduced.

[0232] [Effects] In the secondary battery of Aspect 9-3, the electrode wound body 20 and the outer can 11 are in close contact with each other, reducing the air layer that acts as a heat insulating layer. This results in excellent heat dissipation, and when heat is generated in the electrode wound body 20 during charging, the heat from the electrode wound body 20 is efficiently transferred to the outer can 11. As a result, high heat dissipation is achieved, and safety is improved. Note that, as described above, by inserting the swelling tape wound around the electrode wound body 20 into the interior of the outer can 11 and then swelling it, the secondary battery of Aspect 9-3 can be manufactured without impairing manufacturability.

[0233] (10-1) [Configuration] The electrode wound body of Aspect 10-1, which can be applied to batteries such as lithium ion secondary batteries, is a wound laminate in which a positive electrode, a separator, a negative electrode, and a separator are stacked in this order. In the electrode wound body of Aspect 10-1, the negative electrode is present at the innermost periphery, not the separator. More specifically, the innermost periphery of the electrode wound body of Aspect 10-1 is provided with a negative electrode current collector, such as copper foil, wound multiple times (e.g., three or more times).

[0234] [Effects] According to the electrode wound body of Aspect 10-1, the negative electrode current collector is wound multiple times around its innermost periphery, so that the radius of the innermost periphery of the positive electrode wound around it can be increased. This makes it possible to prevent cracks from occurring in the positive electrode active material layer at the innermost periphery of the positive electrode. This allows for improved areal density and volume density of the positive electrode.

[0235] (10-2) [Configuration] The electrode winding of Aspect 10-2, which can be applied to batteries such as lithium ion secondary batteries, is a wound laminate in which a positive electrode, a separator, a negative electrode, and a separator are stacked in this order. In the electrode winding of Aspect 10-2, the negative electrode is present at the innermost periphery, rather than the separator. More specifically, the innermost periphery of the electrode winding of Aspect 10-2 is provided with a negative electrode current collector, such as copper foil, wound multiple times (e.g., three or more times). Here, when the thickness of the negative electrode current collector is a [μm] and the number of windings is b, it is preferable that a × b be 24 μm or greater.

[0236] [Effect] According to the electrode wound body of Aspect 10-2, the negative electrode current collector is wound multiple times around the innermost periphery, so that the mechanical strength of the electrode wound body can be maintained without using a center pin made of a conductive material such as metal. Because the electrode wound body of Aspect 10-2 does not have a center pin made of a conductive material, it is possible to avoid an internal short circuit caused by the center pin coming into contact with the positive electrode current collector plate, the negative electrode current collector plate, or the like.

[0237] (10-3-1) [Configuration] FIG. 49A is a schematic plan view showing an unfolded state of an electrode winding 20 according to embodiment 10-3-1 that can be used in batteries such as lithium-ion secondary batteries. The electrode winding of embodiment 10-3-1 is formed by winding a laminate in which a positive electrode 21, a separator, a negative electrode 22, and a separator are stacked in this order. However, the separator is not shown in FIG. 49A . As shown in FIG. 49A , the electrode winding 20 according to embodiment 10-3-1 has a portion on the winding start end 20E1 side where only the negative electrode 22 is present and no positive electrode 21 is present. Therefore, in the winding center portion of the electrode winding 20 according to embodiment 10-3-1, only the negative electrode 22 that does not face the positive electrode 21 is wound multiple times (e.g., three or more times). A thin copper plate 22C is attached to the negative electrode active material layer 22B of the negative electrode 22 that does not face the positive electrode 21. The thickness of the copper plate 22C is, for example, about 40 μm. The entire copper plate 22C may be joined to the negative electrode active material layer 22B, or only a portion of the copper plate 22C may be joined to the negative electrode active material layer 22B. In the innermost portion of the wound electrode body 20 of Aspect 10-3-1, the laminate of the negative electrode current collector 22A, the negative electrode active material layer 22B, and the copper plate 22C is wound together multiple times (for example, three or more times).

[0238] [Effects] According to the electrode winding of aspect 10-3-1, in the central portion of the winding, only the negative electrode 22 of the positive electrode 21, separator, and negative electrode 22 is wound multiple times, and the negative electrode 22 in the central portion of the winding has a copper plate 22C. Therefore, even if stress is applied to the innermost portion of the positive electrode 21 of the electrode winding 20 due to expansion of the negative electrode 22 during charging, for example, the innermost portion of the positive electrode 21 can withstand that stress. This prevents buckling of the innermost portion of the positive electrode 21 and cracks in the positive electrode active material layer 21B in the innermost portion. As a result, short circuits within the battery can be effectively suppressed.

[0239] (10-3-2) [Configuration] FIG. 49B is a schematic plan view showing an unfolded state of the electrode winding body 20 of embodiment 10-3-2, which can be used in batteries such as lithium-ion secondary batteries. The electrode winding body of embodiment 10-3-2 is formed by winding a laminate in which a positive electrode 21, a separator, a negative electrode 22, and a separator are stacked in this order. However, the separator is not shown in FIG. 49B. As shown in FIG. 49B, the electrode winding body 20 of embodiment 10-3-2 has a portion on the winding start end 20E1 side where only the negative electrode 22 is present and no positive electrode 21 is present. Therefore, in the winding center portion of the electrode winding body 20 of embodiment 10-3-2, only the negative electrode 22, which does not face the positive electrode 21, is wound multiple times (e.g., three or more times). A thin copper plate 22C is attached to the negative electrode active material layer 22B of the negative electrode 22, which does not face the positive electrode 21. The thickness of the copper plate 22C is, for example, about 40 μm. The entire copper plate 22C may be bonded to the negative electrode active material layer 22B, or only a portion of the copper plate 22C may be bonded to the negative electrode active material layer 22B. Furthermore, a resin tape 22D is provided so as to cover at least a portion of the copper plate 22C. In the innermost peripheral portion of the electrode wound body 20 of Aspect 10-3-2, the laminate of the negative electrode current collector 22A, the negative electrode active material layer 22B, the copper plate 22C, and the resin tape 22D is wound together multiple times (for example, three or more times).

[0240] [Effects] In the electrode winding of aspect 10-3-2, only the negative electrode 22 of the positive electrode 21, separator, and negative electrode 22 is wound multiple times in the winding center portion, and the negative electrode 22 in the winding center portion has a copper plate 22C. Therefore, even if stress is applied to the innermost portion of the positive electrode 21 of the electrode winding 20 due to expansion of the negative electrode 22 during charging, for example, the innermost portion of the positive electrode 21 can withstand that stress. This prevents buckling of the innermost portion of the positive electrode 21 and cracks in the positive electrode active material layer 21B in the innermost portion. Furthermore, because the copper plate 22C is covered with the resin tape 22D, the step between the negative electrode current collector 22A and the copper plate 22C at the edge of the copper plate 22C can be reduced, thereby mitigating local stress applied to the positive electrode 21. As a result, short circuits within the battery can be effectively suppressed.

[0241] (10-4-1) [Configuration] FIG. 50A is a schematic plan view showing an unfolded state of the electrode winding body 20 of embodiment 10-4-1, which can be used in batteries such as lithium-ion secondary batteries. The electrode winding body of embodiment 10-4-1 is formed by winding a laminate in which a positive electrode 21, a separator, a negative electrode 22, and a separator are stacked in this order. However, the separator is not shown in FIG. 50A. As shown in FIG. 50A, the electrode winding body 20 of embodiment 10-4-1 has a portion on the winding start end 20E1 side where only the negative electrode 22 is present and no positive electrode 21 is present. Therefore, in the winding center portion of the electrode winding body 20 of embodiment 10-4-1, only the negative electrode 22, which does not face the positive electrode 21, is wound multiple times (e.g., three or more times). A thin copper plate 22C is attached to the negative electrode active material layer 22B of the negative electrode 22, which does not face the positive electrode 21. The thickness of the copper plate 22C is, for example, approximately 40 μm. The entire copper plate 22C may be bonded to the negative electrode active material layer 22B, or only a portion of the copper plate 22C may be bonded to the negative electrode active material layer 22B. In the innermost portion of the wound electrode body 20 of Aspect 10-4-1, a laminate of the negative electrode current collector 22A, the negative electrode active material layer 22B, and the copper plate 22C is wound together multiple times (e.g., three or more times). Furthermore, in the wound electrode body 20 of Aspect 10-4-1, a thin portion 61 is provided in a portion of the positive electrode active material layer 21B at the inner end of the positive electrode 21. The thin portion 61 is a portion of the positive electrode active material layer 21B that is thinner than the thickness of the portion other than the thin portion 61. The thin portion 61 is formed, for example, by laser ablation.

[0242] [Effects] According to the electrode winding of aspect 10-4-1, in the winding center portion, only the negative electrode 22 of the positive electrode 21, separator, and negative electrode 22 is wound multiple times, and the negative electrode 22 in the winding center portion has a copper plate 22C. Therefore, even if stress is applied to the innermost portion of the positive electrode 21 of the electrode winding 20 due to expansion of the negative electrode 22 during charging, for example, the innermost portion of the positive electrode 21 can withstand that stress. This prevents buckling of the innermost portion of the positive electrode 21 and cracks in the positive electrode active material layer 21B in the innermost portion. Furthermore, because the positive electrode active material layer 21B has a thin portion 61, expansion of the negative electrode 22 near the winding center portion of the electrode winding 20 during charging can be suppressed. As a result, short circuits within the battery can be effectively suppressed.

[0243] (10-4-2) [Configuration] FIG. 50B is a schematic plan view showing an unfolded state of the electrode winding body 20 of embodiment 10-4-2, which can be used in batteries such as lithium-ion secondary batteries. The electrode winding body of embodiment 10-4-2 is formed by winding a laminate in which a positive electrode 21, a separator, a negative electrode 22, and a separator are stacked in this order. However, the separator is not shown in FIG. 50B. As shown in FIG. 50B, the electrode winding body 20 of embodiment 10-4-2 has a portion on the winding start end 20E1 side where only the negative electrode 22 is present and no positive electrode 21 is present. Therefore, in the winding center portion of the electrode winding body 20 of embodiment 10-4-2, only the negative electrode 22, which does not face the positive electrode 21, is wound multiple times (e.g., three or more times). A thin copper plate 22C is attached to the negative electrode active material layer 22B of the negative electrode 22, which does not face the positive electrode 21. The thickness of the copper plate 22C is, for example, approximately 40 μm. The entire copper plate 22C may be bonded to the negative electrode active material layer 22B, or only a portion of the copper plate 22C may be bonded to the negative electrode active material layer 22B. Furthermore, a resin tape 22D is provided so as to cover at least a portion of the copper plate 22C. In the innermost portion of the electrode wound body 20 of Aspect 10-4-2, a laminate of the negative electrode current collector 22A, the negative electrode active material layer 22B, the copper plate 22C, and the resin tape 22D is wound multiple times (e.g., three or more times). Furthermore, in the electrode wound body 20 of Aspect 10-4-2, a thin portion 61 is provided in a portion of the positive electrode active material layer 21B at the inner circumferential end of the positive electrode 21. The thin portion 61 is a portion of the positive electrode active material layer 21B that is thinner than the thickness of the portions other than the thin portion 61. The thin portion 61 is formed, for example, by laser ablation.

[0244] [Effects] In the electrode winding of aspect 10-4-2, only the negative electrode 22 of the positive electrode 21, separator, and negative electrode 22 is wound multiple times in the winding center portion, and the negative electrode 22 in the winding center portion has a copper plate 22C. Therefore, even if stress is applied to the innermost portion of the positive electrode 21 of the electrode winding 20 due to expansion of the negative electrode 22 during charging, for example, the innermost portion of the positive electrode 21 can withstand the stress. This prevents buckling of the innermost portion of the positive electrode 21 and cracks in the positive electrode active material layer 21B in the innermost portion. Furthermore, because the copper plate 22C is covered with the resin tape 22D, the step between the negative electrode current collector 22A and the copper plate 22C at the edge of the copper plate 22C can be reduced, thereby reducing local stress applied to the positive electrode 21. Furthermore, because the positive electrode active material layer 21B has the thin portion 61, it is possible to suppress expansion of the negative electrode 22 near the central portion of the wound electrode body 20 during charging, thereby effectively suppressing short circuits inside the battery.

[0245] (10-5) [Configuration] The wound electrode body of Aspect 10-5, which can be applied to batteries such as lithium ion secondary batteries, has a coil spring-shaped core material CS, for example, as shown in Fig. 51, inserted into its central through-hole. That is, the wound electrode body of Aspect 10-5 is formed by winding a laminate in which a positive electrode, a separator, a negative electrode, and a separator are stacked in this order around the core material CS. The core material CS is formed by winding a plate-shaped elastic member such as stainless steel.

[0246] [Effects] According to the electrode wound body of Aspect 10-5, a coil spring-shaped core material CS is inserted into a through hole at the center. This allows the outer diameter of the core material CS to be adjusted to match the inner diameter of the electrode wound body, allowing the inner surface of the electrode wound body and the outer surface of the core material CS to be in close contact. This allows the core material CS to increase the mechanical strength of the electrode wound body and suppress deformation of the electrode wound body during expansion and contraction. This prevents buckling in the innermost peripheral portion of the positive electrode 21 and cracks in the positive electrode active material layer 21B at the innermost peripheral portion. As a result, short circuits within the battery can be effectively suppressed.

[0247] (10-6) [Configuration] FIG. 52 is a cross-sectional schematic diagram showing an electrode winding 20 and a center pin CP according to embodiment 10-6, which can be applied to a battery such as a lithium-ion secondary battery. The center pin CP is inserted through a central through-hole 26 in the electrode winding 20 of embodiment 10-6. The center pin CP includes a cylindrical core CP-L1 made of a highly rigid material such as stainless steel, and a resin layer CP-L2 covering its outer periphery. The resin layer CP-L2 is made of a resin material that expands upon heating and undergoes plastic deformation at a predetermined temperature (e.g., approximately 130°C). The resin layer CP-L2 can have a three-layer structure, for example, made of polyethylene (PE), polyester, and rubber. The surface of the resin layer CP-L2 is in close contact with the inner surface of the through-hole 26 in the electrode winding 20. In particular, the resin layer CP-L2 is preferably heat-sealed to the inner surface of the through-hole 26.

[0248] [Effects] According to the electrode wound body 20 of aspect 10-6, a center pin CP is inserted into the through hole 26 at the center thereof, and the surface of the resin layer CP-L2 of the center pin CP is in close contact with the inner surface of the through hole 26. As a result, the center pin CP increases the mechanical strength of the electrode wound body 20, and deformation of the electrode wound body 20 during expansion and contraction can be suppressed. This prevents buckling from occurring in the innermost peripheral portion of the positive electrode constituting the electrode wound body 20, and prevents cracks from occurring in the positive electrode active material layer in the innermost peripheral portion. As a result, short circuits within the battery can be effectively suppressed.

[0249] (10-7) [Configuration] Figure 53 is a cross-sectional schematic diagram showing a center pin CP of embodiment 10-7 that can be applied to a battery such as a lithium-ion secondary battery. The center pin CP of embodiment 10-7 has a core CP-1 that is a cylindrical member, an insulating film CP-2 that covers the vicinity of the upper end of the core CP-1, and an insulating film CP-3 that covers the vicinity of the lower end of the core CP-1. The core CP-1 is made of a highly rigid material such as stainless steel. Examples of materials that can be used to form the insulating films CP-2 and CP-3 include polyester, polyamide, polyolefin, polyacrylate, polymethacrylate, polysulfone, polycarbonate, polypropylene, polyethylene, polysulfone, polytetrafluoroethylene, and polyvinylidene fluoride.

[0250] [Effect] According to the center pin CP of aspect 10-7, the vicinity of the upper end and the vicinity of the lower end of the core CP-1 are covered with insulating films CP-2 and CP-3, respectively, so that an internal short circuit of the battery can be prevented even when the center pin CP comes into contact with the top and bottom surfaces of the battery when vibration is applied or in the event of an abnormality.

[0251] (13-2) [Configuration] FIG. 54A is a perspective view schematically illustrating the appearance of an outer can 11 according to embodiment 13-2, which can be applied to a battery such as a lithium-ion secondary battery. The outer can 11 is a container that houses a positive electrode current collector, a negative electrode current collector, an electrode winding, and the like. The outer can 11 is preferably made of a material with high thermal conductivity and high rigidity, specifically, a metal material such as iron. The outer can 11 has a bottom 11B and a sidewall 11W. The outer can 11 according to embodiment 13-2 has one or more recesses 11U on at least one of the outer and inner surfaces of the sidewall 11W. The number, arrangement, size, and shape of the recesses 11U are not limited to those shown in FIG. 54A and can be selected arbitrarily.

[0252] [Effects] According to the exterior can 11 of aspect 13-2, the recess 11U is provided on at least one of the outer surface and the inner surface of the side wall portion 11W, so the surface area of ​​the side wall portion can be increased compared to an exterior can without a recess, resulting in high heat dissipation. As a result, heat generated by the battery reaction of the built-in electrode winding body can be efficiently dissipated to the outside. Therefore, in a battery using the exterior can 11 of aspect 13-2, temperature rise can be suppressed.

[0253] (13-3) [Configuration] FIG. 54B is a perspective view schematically illustrating the appearance of an outer can 11 according to embodiment 13-3, which can be used in a battery such as a lithium-ion secondary battery. The outer can 11 is a container that houses a positive electrode current collector, a negative electrode current collector, an electrode winding, and the like. The outer can 11 is preferably made of a material with high thermal conductivity and high rigidity, specifically, a metal material such as iron. The outer can 11 has a bottom 11B and a sidewall 11W. The outer can 11 according to embodiment 13-3 has one or more protrusions 11T on at least one of the outer and inner surfaces of the sidewall 11W. Note that the number, arrangement, size, and shape of the protrusions 11T are not limited to those shown in FIG. 54B and can be selected arbitrarily.

[0254] [Effects] According to the exterior can 11 of aspect 13-3, the protrusions 11T are provided on at least one of the outer and inner surfaces of the side wall 11W, so the surface area of ​​the side wall can be increased compared to an exterior can without protrusions, resulting in high heat dissipation. This allows the heat generated by the battery reaction in the built-in electrode winding body to be efficiently dissipated to the outside. Therefore, a battery using the exterior can 11 of aspect 13-3 can suppress temperature rise.

[0255] (13-4) [Configuration] FIG. 54C is a perspective view schematically illustrating the appearance of an outer can 11 according to embodiment 13-4, which can be used in a battery such as a lithium-ion secondary battery. The outer can 11 is a container that houses a positive electrode current collector, a negative electrode current collector, and an electrode winding. The outer can 11 is preferably made of a material with high thermal conductivity and high rigidity, specifically, a metal material such as iron. The outer can 11 has a bottom 11B and a sidewall 11W. The outer can 11 according to embodiment 13-4 has one or more grooves 11G on at least one of the outer and inner surfaces of the sidewall 11W. The grooves 11G are provided, for example, around the outer surface of the sidewall 11W of the outer can 11. Note that the number, arrangement, and width of the grooves 11G are not limited to those shown in FIG. 54C and can be selected arbitrarily.

[0256] [Effects] According to the exterior can 11 of aspect 13-4, the groove 11G is provided on at least one of the outer surface and the inner surface of the side wall portion 11W, so the surface area of ​​the side wall portion can be increased compared to an exterior can without the groove 11G, resulting in high heat dissipation. As a result, heat generated by the battery reaction of the built-in electrode winding body can be efficiently dissipated to the outside. Therefore, in a battery using the exterior can 11 of aspect 13-4, temperature rise can be suppressed.

[0257] The present disclosure has been described above using one embodiment and several modified examples, but the configuration of the present disclosure is not limited to the configuration described in the above one embodiment and several modified examples, and can be modified in various ways.

[0258] Although the above description has been given with respect to the case where the electrode reactant is lithium, the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0259] The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

[0260] DESCRIPTION OF SYMBOLS 1...Lithium ion secondary battery, 11...Outer can, 11B...Bottom, 11N...Open end, 11P...Bent portion, 11R...Crimped structure, 11S...Neck portion, 11W...Side wall portion, 11WS...Side surface, 12, 13...Insulating plate, 14...Battery lid, 14T...Convex portion, 15...Gasket, 20...Electrode winding body, S20...Laminate, 21...Positive electrode, 21A...Positive electrode collector current collector, 21B... positive electrode active material layer, 21BT1... first edge, 211... positive electrode covering region, 212... positive electrode exposed region, 212E... positive electrode edge, 21E1... edge on the winding center side, 21E2... edge on the winding outer periphery side, 22... negative electrode, 22A... negative electrode current collector, 22B... negative electrode active material layer, 221... negative electrode covering region, 222... negative electrode exposed region, 222E... negative electrode edge, 22E 1...center axis side edge, 22E2...outer peripheral side edge, 23...separator, 23A...first separator member, 23B...second separator member, 24...positive electrode current collector plate, 25...negative electrode current collector plate, 26...through hole, 30...safety valve mechanism, 31, 33...fan-shaped portion, 32, 34...band-shaped portion, 35, 36...opening, 41...upper end surface, 41G1, 41G2...groove portion, 42...lower end surface, 46...fixing tape, 50...outer tube, 53, 54...insulating tape, 55...washer, 55K...opening, 61...first joint, 61A...first linear portion, 61B...first folded portion, 62...second joint, 62A...second linear portion, 62B...second folded portion, 101...insulating layer, 300...battery pack, CL...central axis, K...boundary.

Claims

1. A laminate comprising a first electrode, a second electrode, and a separator is wound along the longitudinal direction of the laminate, and the electrode winding body has through holes penetrating in a width direction perpendicular to the longitudinal direction, The electrode winding body is sandwiched in the width direction by a first electrode current collector plate and a second electrode current collector plate facing each other. Equipped with, The first electrode current collector plate includes an opening in the width direction that overlaps with the through hole, The diameter of the opening is smaller than the diameter of the through hole. The peripheral edge of the opening of the first electrode current collector plate is provided with a first bent portion that is bent toward the inside of the through hole. The through hole is provided with a first recess, and the first bent portion covers at least a part of the first recess. Secondary battery.

2. The first electrode comprises a first electrode current collector and a first electrode active material layer covering a portion of the first electrode current collector. The first electrode includes a first electrode covering region in which the first electrode current collector is covered by the first electrode active material layer, and a first electrode exposed region in which the first electrode current collector is exposed without being covered by the first electrode active material layer and is adjacent to the first electrode covering region in the width direction, wherein the first electrode exposed region is joined to the first electrode current collector plate. The first recess is formed in a compressed portion where multiple parts of the first electrode current collector in the first electrode exposure region overlap each other. The secondary battery according to claim 1.

3. The first electrode comprises a first electrode current collector and a first electrode active material layer covering a portion of the first electrode current collector. The first electrode includes a first electrode covering region in which the first electrode current collector is covered by the first electrode active material layer, and a first electrode exposed region in which the first electrode current collector is exposed without being covered by the first electrode active material layer and is adjacent to the first electrode covering region in the width direction, wherein the first electrode exposed region is joined to the first electrode current collector plate. The second electrode comprises a second electrode current collector and a second electrode active material layer covering a portion of the second electrode current collector. The second electrode includes a second electrode covering region in which the second electrode current collector is covered by the second electrode active material layer, and a second electrode exposed region in which the second electrode current collector is exposed without being covered by the second electrode active material layer and is adjacent to the second electrode covering region in the width direction, wherein the second electrode exposed region is joined to the second electrode current collector plate. The maximum thickness of the first compressed portion where multiple parts of the first electrode current collector in the first electrode exposed region overlap is greater than the maximum thickness of the second compressed portion where multiple parts of the second electrode current collector in the second electrode exposed region overlap. The secondary battery according to claim 1.

4. The electrode winding body has a first end face that is perpendicular to the width direction and faces the first electrode current collector plate, The first electrode current collector plate includes a first portion extending along the first end face and a second portion projecting in a first direction from the first portion. The length of the joint closest to the second portion among the multiple joints that join the first portion and the first end face, in the second direction perpendicular to the first direction, is equal to or greater than the length of the second portion in the second direction. The secondary battery according to claim 1.

5. A laminate comprising a first electrode, a second electrode, and a separator is wound along the longitudinal direction of the laminate, and the electrode winding body has through holes penetrating in a width direction perpendicular to the longitudinal direction, The electrode winding body is sandwiched in the width direction by a first electrode current collector plate and a second electrode current collector plate facing each other. Equipped with, The outer edge of the first electrode current collector plate is provided with a second bent portion that is bent toward the second electrode current collector plate. A second recess is provided on the outer surface of the electrode winding body, and the second bent portion covers at least a part of the second recess. Secondary battery.

6. The first electrode comprises a first electrode current collector and a first electrode active material layer covering a portion of the first electrode current collector. The first electrode includes a first electrode covering region in which the first electrode current collector is covered by the first electrode active material layer, and a first electrode exposed region in which the first electrode current collector is exposed without being covered by the first electrode active material layer and is adjacent to the first electrode covering region in the width direction, wherein the first electrode exposed region is joined to the first electrode current collector plate. The second recess is formed in the compressed portion where multiple parts of the first electrode current collector in the first electrode exposed region overlap each other. The secondary battery according to claim 5.

7. The first electrode comprises a first electrode current collector, an undercoat layer covering the first electrode current collector, and a first electrode active material layer covering a part of the undercoat layer. The second electrode comprises a second electrode current collector and a second electrode active material layer covering the second electrode current collector. In the width direction, the edge of the first electrode active material layer is located recessed from the edge of the undercoat layer, and the edge of the second electrode active material layer is located between the edge of the undercoat layer and the edge of the first electrode active material layer. A secondary battery according to claim 1 or claim 5.